How can mouse-actions be recorded in Configure Keyboard Shortcuts?

I would like to configure my muscle-memory-shortcuts from Photoshop like eg. Ctrl+left-mouseclick - but the mouseclick doesn’t seem to be accepted by Gimp?

At the same time Alt+left-mouseclick actually shows/hides the layer mask in Gimp - it’s probably installed with PhotoGimp - but! this working combination is not shown in Configure Keyboard Shortcuts, where “Show Layer Mask” has status “Disabled”.

How can I make Gimp accept and show my mouse-actions for shortcuts?