behaviour of an master artboard with styles and grid would be great. Integration of symbols or pinned objects like indeed navigation would be also great. In every screen you must be able to override the items if you like to...

As a designer I want to create one editable header navigation instance and repeat that across all pages to allow very fast flow and navigation management. Similar to photoshops smart object except with links tied to specific art boards.

+1 for mimicking Illustrator 'symbols' OR Photoshop 'smart objects'
ie. Yep to master objects and instances of that object

-1 for mimicking InDesign 'master pages'
ie. Nope to master pages with instances of that page

"Pinned Object" sounds a lot like the "Pin to Browser" feature in Axure.
As a designer creating a prototype I want to have an element such as a global navigation element showing across artboards and not scrolling while the rest of the elements in the dartboard move.

Master artboards, master components, master pages. All of these things have one thing in common, objects or templates with global effect. Being able to change a component on a single master page/artboard means that anything with a similar layout would be easily changed across a flow. Additionally, allowing for nested master objects and master templates within templates allow for core templates and objects to created that have a wider spread while having modifications made for flows with narrower use cases yet these cases need to be just as "global" as others. As for how it applies to prototypes, this means that once you set both designs and interactions in these master elements, you won't need to repeat existing animations, interactions and modes of operation.

As a designer, I would like to have a master artboard to have an element on all artboards in Design mode as well as in Prototype mode but with an extra feature that will include a common interaction that will be placed for all artboards.

For example, I would like my main navigation to be sticky and decrease in size as the user scrolls down past 300px in length of the site. This can be done by clicking on that element on the master artboard in Prototype mode and have an option to make it sticky, and drag the wire down to 300px on the page which then you can manually or automatically decrease the height/size of the main navigation. This should also automatically make the navigation go back to original state as the user scrolls back up the page (it should detect Point A to Point B and Point B to Point A so to speak).

Just some ideas to throw out there because I completely agree to have master artboards.

Agree, for my use case this can also be applied to how Flash used to have "symbols" and or "smart objects" in illustrator, the ability to have an object, group of objects be created and named accordingly and be able to be editable globally with just one edit to the master object and have this change be applied to all instances that this object is being used within a prototype.

Would it be possible to have a layer-type feature just for the pages? It would go a long way in keeping the prototype organized in design mode.

Agree with everyone here. Making global changes to common elements would be as handy as the repeat grid. Hopefully it could also mean that they could sit 'above' transitions too, so you aren't sliding the same navigation over the top for example.

Fixing regions can be as simple as selecting a region with a selection tool (drawing a box around it) and being able to designate the region as fixed, then linking the fixed region to all the artboards in which it needs to remain fixed (similar to how XD works when linking one artboard to another).

Similar to InDesign, I agree. Including command-clicking an master-artboard item on a regular artboard would unlink it. That way you could locally modify it.

I would think this would function the same way master pages work in InDesign or Muse. Master items, by their definition, are going to function the same way regardless of which screen you're on (think main navigation; buttons along the bottom for an iOS app or links across the top for a web page). I would setup my global items on a master artboard and whatever actions I attach to this global item would work the same way on whatever regular artboard they were used on. If I want to edit the actions of a global item I would need to go to the master artboard they originated from. I don't know if t's absolutely necessary but allowing master artboards to be based on one another like they can InDesign could make things easier for more complicated situations. Allowing global items to be unlocked from the master, similar to InDesign, might also be useful but I can't think of any situation off the top of my head.

I would suggest this just follows the pattern of symbols in Illustrator. For example, add a logo to an art board, then make it a 'symbol', every instance of that symbol across all art boards now can be changed with just one tweak to the symbol.

One ring to rule them all!

In prototype mode, it'd be great if there were an option to set navigation between multiple art-boards without manually dragging the art-board connections.

User Story:
I want to create a left-aligned webpage navigation area which contains six clickable buttons. Each button on the navigation goes the same art-boards, regardless of which art-board the navigation exists on. I want to be able to edit this navigation area in one place, and have changes apply to all art-boards. I want to be able to right click on an element and choose which art-board a user navigates to from a list.

Currently I would need to copy/paste the nav element to each art board, and manually connect each nav element to each other art board. 6x6 navigation = 36 manual connections (my projects are enterprise-focused and commonly have 10-20 elements in a navigation area, each of which would need to be updated and checked each time I add / remove a page during prototyping).

Axure has this feature and it's called "Masters."

I agree with other comments here. When I was creating a prototype I had over 13 art boards and when I was done I decided on a change which I had to apply to all of the boards. It would have been better to have the ability to use a master art board. But in my mind it's possible that you would have multiple master art boards because the navigation could look different among different screens. One art board may not want to use the master header. By having multiple master boards I could link which art boards apply to that master board. Maybe use a different color line to represent that boards 1-5 connect to this master A, boards 6-8 connect to Master B

I +1 this feature. Particularly for simplifying the prototyping process.

If you have a navigation bar that appears in multiple artboards you'll end up in a pickle trying to keep track of it all. Not having this feature limits the scalability of projects somewhat. Especially regarding artboard organization and hierarchy.

Suggestion
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-I'd image you be able to create an object in an artboard (maybe even a special 'assets only' artboard) and in the prototype panel set it as a 'Constant' or 'Master' element.

-There can also be sub-elements in the 'Master' element that you can map to any artboard you want.

If 'fixed position objects' and defined 'scrollable areas' are included this would sync very well with those.

@Max Neuse no they're pretty different. That post is similar to editing 'Instances' of the same object. Like if you created a 'style' and wanted to edit it's features across multiple artboards.

Similar to Muse's Master pages, and library palette, so that there is an A, B, C, etc. to either click on a regular page, right click and select "apply a master page" or drag out from the master page area and place over top the intended page to follow a master. I also Like the library object setup on Muse.

I LOVE this feature from Principle App.

"Animation Mappings:
If two layers on different artboards have the same name, Principle will treat the layers as if they are the same, and will automatically animate between them. If there is not a layer with the same name on both the source and destination artboard, the layer will simply disappear or appear with no animation."

As a designer creating a design, I’d like to have the same element showing up in different artboards, so that I can change the style (color, font, size, etc.) of that element globally to cut down labor time for incremental changes.

As a designer creating a design, I’d like to have the same element showing up in different artboards, so that I can change the anchor points of that element globally to cut down labor time for incremental changes.

As a designer creating a design, I’d like to have the same element showing up in different artboards, so that I can change the x and y coordinates of that element globally to cut down labor time for incremental changes.

As a designer creating a prototype, I’d like to change transitions globally so that I can fine tune or change a transition across all artboards with ease