I get an error when I click “Start” after I open Shotcut.
version 18.11.18.02
I have tried multiple locations, all have my user ID as the owner with rwx permissions. I have no other issues with any other application or file system permissions.
It has a fix in this area: Fixed making project folder if a parent folder does not exist.
I am not sure if this is the problem you faced, but I could not reproduce it, and this is the best guess I came up with. If you know any Qt API, I can point you to the place in the code if you want to look for an obvious problem.
Also, maybe this problem is specific to the Flatpak build, container, or runtime version. @pete might know something about that.
It seemed to be fixed, however after creating a project successfully, manipulating some video, I went back in to create a new project and I am getting the error again.
Look at the GitHub big report above. It links to a bug in the KDE bug tracker that shows a KDE component that is infecting the strings in applications! I think your experience confirms this may be the source of this bug (not necessarily Flatpak). The KDE bug report has a workaround that you can try.