EDIT: This doesn’t really fix it. Setting “Use Mouse for Touch” changes click behaviour alltogether.
I just found out what resolves this issue for me (I don’t know why though).
- Go to Project Settings > Engine - Input.
- Under Mouse Properties, check Use Mouse for Touch.
This toggles setting “bUseMouseForTouch=True” in DefaultInput.ini - now setting “Default Viewport Mouse Lock” works as intended, as well as using “Set Input Mode…” nodes.
Cheers!