You can export custom UMG widgets as a texture output node on Reality Editor.
The widget class must be derived from ZDRealityWidget class.
Implementation



The parent class ZDRealityWidget is required.



Launch Reality Control and press F7 to launch Reality Setup.
Click PLAY on Reality Editor.

Open Reality Setup. Click CREATE → EXPERIMENTAL → WIDGET → WIDGET

You can use widget as image/video output on Reality Setup.