Hi teedee - there used to be an app called lxscreenshot that I used that was from an ubuntu ppa (specifically really for lubuntu). I dont even know if its maintained anymore and have not looked since making the change to Debian.
I have trended towards simplifying my life and desktop and now I use scrot.
Its a command line tool, but you can also run it from the "run" dialog box in the menu and simply type the word 'scrot' and it takes a screenshot of whatever you have open and places it as a png in your home directory with a date time stamp. good for quick shots of something you want.
Then I use shotwell if I want to crop it, or convert to jpg, scale, etc.
tks,
biff