How to add a key to an empty schema? [closed]

I would like to automate setting some settings, specifically add some keyboard shortcuts to ~/.config/dconf/user. Here is how it looks in dconf-editor:

Now gsettings (or dconf) can list the first one:

$ gsettings get org.cinnamon.keybindings custom-list
['custom0', 'custom1', 'custom2', 'custom3']

However, I cannot see a way to then add a new keybinding, or even to read the customX keys.

$ gsettings get org.cinnamon.keybindings.custom-keybinding:/ custom0
No such key 'custom0'

How can I add, for example, a custom4 key with binding='<Super>g', command='geany', name='Geany'?

Output to Donarssons answer:

$ gsettings get org.cinnamon.keybindings.custom-keybindings:/custom0/ binding
No such schema 'org.cinnamon.keybindings.custom-keybindings'
$ gsettings get org.cinnamon.keybindings.custom-keybinding:/custom0/ binding
''

And screenshot after the following command. Note that custom4 does not go to custom-keybindings but to the root.

gsettings set org.cinnamon.keybindings.custom-keybinding:/custom4/ binding '<Super>g'

I'm using Linux Mint as my O/S.

It's a syntax error. This should work:

$ 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

To set a new hotkey:

$ 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'