I came accross the issue that a copied Express Form is not editable.
I search the net, and found it already was in the bug tracker.
I digged a bit deeper and found a quick fix to resolve this issue.
I have put my solution in the bugtracker for those who want a quick fix.

Go to https://www.concrete5.org/developers/bugs/8-1-0/unable-to-edit-copie... to resolve it quickly.

I do think there is a better way to solve this.
But if you come across this, it can be easily fixed for now :)
Thought I let you guys know.

Thanks!