Install xkeycaps by entering the following commands in the terminal:
sudo apt update sudo apt install xkeycaps
Description:
manipulate X11 keymaps (for xmodmap) graphically
xkeycaps is a graphical front-end to xmodmap(1). It opens a window that looks like a keyboard; moving the mouse over a key shows what KeySyms and Modifier bits that key generates. Clicking on a key simulates KeyPress/KeyRelease events on the window of your choice. It is possible to change the KeySyms and Modifiers generated by a key through a mouse-based interface. This program can also write an input file for xmodmap to recreate your changes in future sessions.
Homepage: https://www.jwz.org/xkeycaps/
Version: 2.47-5
Section: universe/x11