We have Linux Mint Cinnamon installed on our laptop computer. My b/f was using the computer, trying to change the file names of some files in a folder when he caused something to change. I don't know how to change it back.

He right-CLICKED on file names then selected "rename" then proceeded to place the cursor where he wanted within the file name to type in additional stuff when he somehow did something that then caused where ever you placed the cursor to change to a highlighted space. For example if you clicked on a letter or even a space then that letter or space would then be highlighted. I tried to figure what setting he changed so I could change it back to default but I never encountered this so I didn't know what it setting it was. I right-clicked on the file's name during the re-naming process and noticed there was another menu popped up so I clicked on other selections for "input method" on the menu and then it got worse. Now the whole file name highlights in black when you CLICK "re-name". Does anyone know how to FIX this? Selecting another setting did not make it go away. We just want it to go back to a STRAIGHT line cursor like it usually is.Not sure if you found your solution or not.... but it sounds like he hit the "Insert" key. It's usually located on the keyboard somewhere above the Return key (aka Enter) or the num pad.

Hitting that key does cause the highlighting you are are talking about. It also deletes 1 character for every character you type.
To undo it, just click the insert key again. And undo the other settings you changed. Hope this helps! I think that I know of what issue you are referring to....
Please try changing the theme to a different one and see if the issue persists!
and please let me know it that did it or not?

Blair