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

I was thinking of something similar to Muse's Master pages. You could have a master art board or object that will cross all artoboards.
For example, a navigation bar. It would save so much time if you could specify which button takes you to which page once, and not in every panel in every page.

“As a designer creating a prototype, I'd like to make a common element navigate a certain screen from all instances, so I can simply create the main navigation structure"
and
"As a designer creating a prototype, I'd like to be able to overwrite common element navigation in a specific screen, so I can easily adjust my main navigation structure"

Let's use a global header bar that is being used across all artboards. This should be able to be defined as a "proto-object" (symbol or style.) If the proto-object is changed on one artboard, it is modified on all the boards. I.e. If one changes the color of the header bar in one artboard, the new header color mirrors across all artboards with the proto-object.

One would also need the option to unattach a proto-object so that if on one specific artboard a different version of that object is needed, say a different color, it will not be affected by or affect the other proto-object.

And a proto-object should include any selected elements. Like if the header bar had text-based menu items, icons, etc. and they were all selected and turned into a proto-object then a change to any of the nested elements would mirror as well.

I think this duplicates https://adobexd.uservoice.com/forums/353007-adobe-xd-feature-requests/suggestions/12869085-global-style-edits or?

Do you think about something similar to a smart object? If so, yes definitely!

I notice I do a lot of copy pasting between artboards (automatic "Paste In Place" s awesome btw). It would be nice if I could right click an existing artboard and do "Create new artboard from this...", and thereby creating a new artboard identical to the previous. The artboards could then inherit from each other in a tree-like structure, so that changes to a parent-artboard would be reflected throught it's children. This is especially useful for changing repeated elements like menu icons, fonts and background colors that are repeated over multiple artboards.