Group layers within categories in overlayGroups parameter in addLayersControl function

[PauloJhonny]

Hi,

I would like to know please if it is possible to group layers within categories ("Landmarks" and "Random" in the example below) in overlayGroups like this:

Source: https://github.com/ismyrnow/leaflet-groupedlayercontrol

And if each category had a plus button to open/hide layers list, it would be amazing too.

Thank you so much!