How to change UI size in Unreal Engine 5
If you have a 4k display you may have problem with ui size in unreal engine 5. In UE 5.4 they added application scale slider to the editor preferences. You can find it in Editor Preferences > User Interface > Application Scale. If you have version older than 5.4, there are two ways to change it.
Widget Reflector
The simplest but temporary method is to use widget reflector, you can find it in Tools -> Debug -> Widget Reflector, or press Ctrl + Shift+ W to open it. In Widget Reflector we have “Application Sca le” slider. Unfortunately this is temporary, to change it permanently we need to use a plugin.