Comment 6 for bug 1070004

As far as I can tell this bug still hasn't been fixed (at least, with all updates installed, I still can't save in another folder than the ones listed in the dropdown). Here's a workaround, hope it helps somebody else:

1) Using nautilus (haven't tried this with other file managers), navigate to the folder you would like to save to
2) Choose Bookmark -> Add Bookmark
3) The folder now shows up as one of the options in the drop down within openshot (you may have to restart openshot to get it to appear)

After the first save, you are clear to delete the bookmark (so things don't get cluttered/messy). Hope this helps!

Any word on when this will get sorted out/pushed to Ubuntu updates or however that works?