> Right click on the selection dot is already being used for something else - it isolates the item removing selection from other things.
Well, then might Shift-Right-Click invoke an inverse select … select all such "other" (unselected) things instead?.

> How would collapsing like this be preferable to clicking on the +/- box?
When the list is very long, I have to scroll to the +/- box

> I'll see about having individual names reported similar to how it shows multiple styles.
Once I click on a style, that style remains in the selection and all the other styles immediately disappear from the list.
Is there any way to do multiple selects of both styles and/or names?
Checkboxes?

Maybe a small button [⁝] could remain unaffected by scrolling to be ever available with a range of such functionalities and room for more in the future, rather than the context menu that I had initially suggested.