I would like to ask is that UI Builder is only use for creating runtime UI or it also can use for creating editor UI?
You can create both Runtime UI and Editor UI with the UI Builder.
Check out this manual page for some details: https://docs.unity3d.com/Manual/UIB-getting-started-editor-ext.html
1 Like
Does it means that I use UI Builder to create an UI panel I can just directly use it at both editor and runtime without needing to do any changes?
The same UXML/USS files can be used in both contexts. The main caveat is that you can’t reference some UnityEditor-only controls, just like you can’ use UnityEditor.* APIs in the Runtime.