UMG supports automatic scaling for resolution-independent UI. There are default DPI scaling settings applied to every project. You can configure it by the Project Settings menu under the User Interface section. You can change Application Scale value via the input box, choose option of DPI Scale Rule and adjust DPI Curve.
You can set the DPI Scale Rule to one of four options:
Shortest Side: 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: Evaluates the scale curve based on the X axis of the viewport.
Vertical: Evaluates the scale curve based on the Y axis of the viewport.
Right-click on the DPI Curve graph allows you to add points to the curve by selecting the Add Key option. After that you can set the resolution and its corresponding scale value via the input boxes. Also, you can supply an external Float Curve or create a Float Curve based on the currently applied settings by expanding the DPI Curve option.