My install of Kdenlive appears to be stuck in Fullscreen mode. Ctrl+Shift+F removes or places a check mark in the "Fullscreen"/"Exit FullScreen" option under the "Settings" menu.
Window controls are missing so I can't minimize, resize or close the window.
I have removed and reinistalled kdenlive, purged --autoremoved kdenlive and each time I have tried a different source (one of two different ppa's and from the Mint repository).
However, every time I reinstall, my layout (View -> Load Layout) is an option. Not sure how this can be if I've completely removed everything

kdenlive 16.04
Mint 18
Dell XPS 15 i7 w/fhd


Screenshot:

I FINALLY found kdenliverc in /home/USER/.config.
Deleted the file and started Kdenlive. It started up like a fresh install.

Slight necrobump; however, this may be useful to others. I also experienced this issue. I will raise a bug against the project when I have a moment (unless there already is one), but in the meantime the following worked for me:

Edit the config file ~/.config/kdenliverc and remove the Height line from the [MainWindow] section. This approach has the advantage of not losing ALL of your settings (though deleting the config file as suggested above certainly works too). Ensuring that you exit fullscreen prior to exiting kdenlive will prevent the issue from reoccurring.

I haven't seen any other issues from this approach though I can make no guarantee.