I received this pop up while attempting to load a Jpg image file I had just downloaded. It says: "... Ambiguous Shortcuts There are two actions (Cut, Delete) that want to use the same shortcut (Shift+Del). This is most probably a bug. Please report it in bugs.kde.org ..." I had double clicked using the track pad button on a Thinkpad, and afterwords I noticed that the setting for clicking with the trackpad was still defaulted on. I am testing Mint 18.2 Sonya beta w/ KDE 5 as a USB live OS right now. I don't know if the system thought I was trying to click with the trackpad itself as well at the same time? I don't believe I hit shift+del so I don't know why this pop up claims I did. All I did was left double click to open the image. This pop up seems to happen whenever Gwenview loads. I tried to submit this bug without a version number, opened Gwenview to get the version, and was prompted with a duplicate warning popup. It's version 16.04.3 Hope this helps.
*** This bug has been marked as a duplicate of bug 377880 ***