In SDK3 2021.03.22.18.27, SendCustomNetworkEvent was updated to work in editor, by bypassing the SendCustomNetworkEventHook. In doing this, it allowed networked events to work overall, but does not block events that begin with an underscore as the VRChat client does.
Please add an editor only implementation of SendCustomNetworkEventHook instead of removing the code that calls it. This way extensions like CyanEmu can also handle extra details.
Example graph tested without CyanEmu:
application/vnd.unity.graphview.elements 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