UMG supports automatic scaling for resolution-independent UI. There are default DPI scaling rules applied to every project which configured as you see fit from inside the Project Settings menu under the User Interface section.
For the DPI Scale Rule, you can set this to one of four options:
Shortest Side - Which evaluates the scale curve based on the shortest side of the viewport (Most Common Setting).
Longest Side - Evaluates the scale curve based on the longest side of the viewport.
Horizontal - This evaluates the scale curve based on the X axis of the viewport.
Vertical - This option evaluates the scale curve based on the Y axis of the viewport.
You can add points to the curve by Right-clicking and selecting the Add Key option. When clicking on a Key on the curve, you can set the resolution and its corresponding scale value via the input boxes. Also for the curve, you can supply an external Float Curve or create a Float Curve based on the currently applied settings by expanding the DPI Curve option.