Prevent user from accidentally press "Save & process" in Video Editor multiple times

Steps to reproduce:
1. Open Video Editor
2. Select "Publish" at the bottom right
3. Press on "Save & Process"

Actual Results:
After pressing "Save & Process", the user can press the button again and again. Since no message is indicating that the first press of the button did start processing, impatient users tend to press the button again and thereby start the processing multiple times

Expected Results:
Once the user has pressed the button (and therefore started the workflow), the button should become inactive.

Workaround (if any):
Ask users to not press the button multiple times.