The compose key it's defined to do key combinations. It's Used to produce special characters like tildes and accents. To see the list of key names open /usr/share/X11/xkb/rules/xorg.lst and search for "compose".
This technique was tested in Lubuntu. Two ways to enter special characters:
- Call setxkbmap to define compose key in the current session
- Define compose key permanently
1). Command line $ setxkbmap -option "compose:rwin"
. Example to define compose key right 'Win'.
2). Open file /etc/default/keyboard and add line XKBOPTIONS="compose:rwin"
(requires restart).
Example to write character ã after defining compose key. Press the compose key, then key 'a' and finally the tilde (AltGr + 4).
https://www.eovao.com/en/a/special%20characters%20ubuntu%20linux/5/how-to-enter-special-characters,-accents-and-tildes-in-ubuntu
gucharmap
. Applications -> Accessories -> Character map.gsettings set org.gnome.desktop.input-sources xkb-options "['compose:ralt']"
. Source askubuntu.com/a/784005/25388