I have a selectlist I'm designing that allows you to select multiple levels simultaneously but the trouble is that the nesting is infinitely deep. It works fine for about 3 levels:

but after that the idea of managing it with indentation and font sizes seems ludicrous as it could be infinitely deep.

Any thoughts or examples would be greatly appreciated.

I'm designing a selectlist that allows you to select multiple levels simultaneously. It works fine for up to 3 levels:

This is just an example, in some instances this model would accommodate product selection which can have pretty deep nesting, about 10 levels, in various categories. Beyond 3 levels, the idea of managing nesting with indentation and font sizes seems ludicrous as it could be infinitely deep.

Any thoughts or examples would be greatly appreciated.