I'd like a filter option on the spell listings where you can exclude a class (e.g., spells not available to Bards). Of course, you would want to be able to combine this with the current "available to class" selection(s).  This would be useful for 1) bards selecting magical secrets, and 2) when trying to explore the options that a multiclass caster combination provides (e.g., available to Ranger but not available to Druid.)

Another related option might be spells exclusively available to a class.

Agreed. And filter by spell duration.

I think we need exclude/include filters on everything. The best method I've seen implemented so far is on spell components where if you click once, it's to find spells with those components, but if you click twice, it's to find spells without that component. I'd love to see that option on every filter.

Also, boolean in global search.

And search within single sources.

This would be incredibly helpful when making sub-classes with extended spell lists.

And for features that let you learn spells from other classes.