Add action to change input source

I want to use caps lock to change input sources languages. Even though macOS does provide this feature out of the box it works surprisingly bad. If I type too fast and hit caps lock, the language is not changed - the hit is simply ignored.

So instead in macOS settings I assigned "Select the previous input source" action a shortcut Opt+Space and then in BTT assigned an action to hit Opt+Space when caps lock is hit. It works much better - now the input source is reliable switched.

However, I am unhappy with this "proxy" shortcut Opt+Space and would like to be able to select an action "switch input source" in BTT directly when I hit caps+lock.