Error log:
---
Assets\VRCSDK\Dependencies\VRChat\Editor\Components3\VRCPlayerStationEditor3.cs(33,40): error CS0234: The type or namespace name 'Udon' does not exist in the namespace 'VRC' (are you missing an assembly reference?)
---
Environment: VRCSDK3-2020.03.10.12.47
Note:
Line 33 accesses VRC.Udon.UdonBehaviour type. So installing Udon SDK clears this error.