It'd be super helpful if I can design for one screen size and XD generates the design for all the other common screen sizes. Not statically, but also allow me to edit design or breaking points on those different screen sizes without actually having them on my canvas taking size and space. Just like Device Mode when it comes to web development using Chrome or Android Studio. And in order to achieve that, we'll be needing percentage sizing option.

Why is this valuable to me?

Most of the time my projects require double the speed, fast sprint and really short time to deliver (close deadlines) and I don't have the time to specify how my design should look in different screens.. SO.. unnecessary mistakes occur when implementing, which slows down our sprint.

Please tell me this has been already considered.

Not only widht and height, but x and y positions too. And XD should keep the values as percentage so that devs can see them!

I am trying using XD but I have always to move using Sketch for a quick operation like reduce 50% of the size.

Yes agree

I agree. I love the Transform command menu that also let's you enter a percentage % number to transform something. I work on projects all the time where we need precise increments like (50%, 25%, 200%, etc.) It would be great to have that as an option.

was a shortcut the scaling of the screen

scale tool capable of scaling object by %

See also https://adobexd.uservoice.com/forums/353007/suggestions/12992463-support-math-operators-in-number-fields

What are the percentages relative to? Artboards make the most sense, but there would need to be a fallback/default incase an object isn't placed on an artboard. Do you have any ideas for what this should be?