Looks pretty cool, even if I'm not sure I would need it.
Didn't see the PR, so no remark about that (for once
About this feature specifically :
* You should use endpoint/endpoint perpendicular constraints rather than curve/curve ones. This would make the sketch more readable
* What happens when arc center distance to line is set to 0 ? You should not use a distance of 0, but a geometrical constraint
More general remarks :
* When you test your features, you should always disable "Auto remove redundant" because having it enable may hide problems
* "Tool setting" seems to me something that users are demanding. I think you should first polish the code of it and submit a dedicated PR. Could be good that user can choose to have it disabled, or present in the Task panel (as now), or popping up as a floating widget