Comment 17 for bug 1880411

I didn't see anybody post this workaround yet, but on my systems, it's possible to get the desired functionality, if you make the config change using the command line. This bug is still relevant though, as its impossible to make the same change using any of the GUI tools.

Pick one of the following commands. Just pick whichever method tickles your inputs the most:

# Make the change with gsettings...
gsettings set org.gnome.shell.keybindings toggle-overview "['<Super>s','Super_R']"

# Or if you are using a more recent release, make the change using dconf write.
dconf write /org/gnome/shell/keybindings/toggle-overview "['<Super>s','Super_R']"

# Finally, if you prefer to use docnf load (good scripts making lots of changes):
dconf load -f /org/gnome/shell/ <<-EOF
[keybindings]
toggle-overview=['<Super>s', 'Super_R']
EOF