After the few times I’ve used Unity, I noticed how much of a pain it is to make the UI elements scale to the screen. Is there any sort of button or feature I missed to make the scaling widget scale automatically to the element?
Look at your Canvas Scaler in the Inspector, and go to scaling mode (or something like that). There should be the following settings
Constant Pixel Size
Scale With Screen Size
Constant Physical Size
You want to use Scale with Screen size, that way a huge UI element won’t cover the screen on lower res 
Ninjapro2k_ meant, this.
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This is a tricky question, since i have found no definitive answer