V1.07:
-constraints are now created instantly, instead of creating them over time and displaying a progress bar. I've done some testing and it seems spreading the load is not that necessary
-removed the "recreate constraints" option, constraint recreation is now always enabled.
-removed warning label about losing constraints
-added constraint recreation to undo and the Physical Unparent tool
-general constraint recreation improvements
-wires attached to target entity should now stay on after physical parenting

A lot of the stuff is still "work in progress" so things may not work perfectly. But overall, adding physical parenting to existing contraptions should now be fairly seamless.
If you find bugs post them in the bug reports thread and I'll try to fix

V1.06.1 - Fixed getting stuck in constraint recreation screen

V1.06:
-added custom toolgun screen
-added option to recreate base entity constraints
-fixed unfrozen base entities getting flung to some direction on undo
-fixed bug that would prevent pasting dupes in some cases after reloading scripts

V1.05.3:
-fixed a parenting error case
-fixed wire entities attached to base being deleted on unparenting in some cases

V1.05.2 - Fixed minor issue where you could select already parented props in some cases

V1.05.1 - The last update didn't fix the problem in all cases, this should

V1.05 - Fixed wire entities connected to the base being removed upon physical parenting

V1.04:
-Fixed visual bug when undoing physical parents caused by the last update
-Fixed some stats of a base entity not persisting through a dupe unless the stats were set after physparenting (such as weight)
-Blocked selecting certain types of vehicles as a physparent target, since it was causing a game crash

V1.03 - Fixed several cases that could cause server crashes

Fixed error when changing unparent area radius