Removing the folder tree without wanting it

Hello, I have a standard view opened (folder tree on the left + folder content on the right).
When I press F8 which is a shortcut I made with my keyboard to open a specific folder, the new window and the initial one appear without the folder tree on the left. Really annoying. How can I fix this please ?

What command(s) does your F8 hotkey run?

F8 is the default hotkey for toggling the folder tree, so if you have not removed that you may be doing both at once.

Thanks Leo ! I guessed it was something like that. Could you please tell me how to deactivate this F8 shortcut in D.O. ?

Settings > Customize Toolbars > Keys.

Always prompt and efficient, many thanks Leo!