É um erro de sintaxe. Isso deve funcionar:
$ gsettings get org.cinnamon.keybindings.custom-keybinding:/org/cinnamon/keybindings/custom-keybindings/custom0/ binding
<Super>e
$ gsettings get org.cinnamon.keybindings.custom-keybinding:/org/cinnamon/keybindings/custom-keybindings/custom0/ command
nemo
$ gsettings get org.cinnamon.keybindings.custom-keybinding:/org/cinnamon/keybindings/custom-keybindings/custom0/ name
nemo
Para definir uma nova tecla de atalho:
$ gsettings set org.cinnamon.keybindings.custom-keybinding:/org/cinnamon/keybindings/custom-keybindings/custom4/ binding '<Super>g' &&
gsettings set org.cinnamon.keybindings.custom-keybinding:/org/cinnamon/keybindings/custom-keybindings/custom4/ command 'geany' &&
gsettings set org.cinnamon.keybindings.custom-keybinding:/org/cinnamon/keybindings/custom-keybindings/custom4/ name 'Geany'