Thanks Daren for your answer,
I thought maybe a workaround for Revit to be active while the add-In is runninng can be the following:
Do you think it is a smart idea to disable the buttons on the Add-Ins Ribbon so the user can still select elements in the Active View But can't press the buttons to prevent creating new event loops.
That brings me to another question, I don't know how to disable the buttons on the Ribbon.
I guess I need the following, but I don't know how to find specific buttons to disable. I know form.showDialog() just block the entire Ribbon.
But maybe I can also use this:
Autodesk.Revit.UI.RibbonButton.Enabled
Anyway, now I'm rambling.