Thanks for the replies. I should have elaborated more.
I'm indeed trying to joint constraint an object (bolt in example) to that point in an assembly. I have managed to do this on circular edges so far.
I put these user selected edges in a list. After the selection is done the user can hit the place button. On all the selected positions/edges I will place a bolt and joint constrain them.
What I'm missing is an option to add this slot centerpoint to my list of objects. How can I let the user add this position/point to the list and preferably have this shown in the modelspace like how the joint function works mentioned in my previous post.
Screencast:
https://knowledge.autodesk.com/community/screencast/832ff849-71e3-4504-a6ff-7cf177c2f613