I would love a checkbox somewhere in the SDK that would allow me to "pause" the evaluation of all VRC Constraint components when not in play mode. If this interferes with setting up constraints, then perhaps the individual constraint should also be un-paused when the constraint is open in the inspector.

Working with constraints gets very messy when working with prefabs because of all the transform overrides generated by the constraints. It's bad to have unnecessary transform overrides inside prefabs not only because its messy but also because it prevents modifications to those transform in the source files from propagating through the prefab inheritance. This is made worse by VRC Constraints because they always mark new overrides, even if the last ones are applied (unlike Unity Constraints).

Personally I would basically always have this "pause" enabled, but it should be default off so that people don't unknowingly think their constraints are broken.