First of, unreal works by default like you want it to.
Scaling the whole thing up or down to fit.
Mind you, it’s done badly so it isn’t pixel perfect. This is most noticeable with grid items.
Anchors should always be top left. And your component needs to be given the proper fixed with values.
If you do that, it will be forced to scale up and down as a whole.
Arguably not the best behavior when pixels matter. You have no control of the distortion introduced via scaling.
Zooming in and out is not the way to test different sizes.
There are controls on the top right - though when testing I just launch a level in an external process in windowed mode, and resize manually. So I know what it looks like…
Worth noting that most end users only see the game at 1 res.
Meaning you’d have no idea how stuff scales or changes between mobile and desktop in 99% of cases.
On top of the mobile ui often having to be completely different.