Are you comfortable with code? I made a repository that tries to simplify it for temporary usage. I needed it for my own personal stuff.

Defining the shortcuts looks like the following.

let alt_shift_shortcut = CosmicKeyboardShortcut {
    modifiers: Modifiers::new().alt().shift(),
    keyboard_key: None,
    action: shortcuts::Action::Spawn("cosmic-term".into()),
    description: Some("Write a description".into()),
};

println!(
    "{:?}",
    add_custom_cosmic_shortcut(alt_shift_shortcut, /* overwrite: */ true)
);

let win_space_shortcut = CosmicKeyboardShortcut {
    modifiers: Modifiers::new().logo(),
    keyboard_key: Some(Keysym::from_char(' ')),
    action: shortcuts::Action::System(shortcuts::action::System::Launcher),
    description: Some("Write a description".into()),
};

println!(
    "{:?}",
    add_custom_cosmic_shortcut(win_space_shortcut, /* overwrite: */ true)
);

The code is available here