As other have pointed out we can now construct what we may call “compound filters”
In my view the “Conceptually easy to understand idea” is that of the subfilter operator.
Eg;
filter +[subfilter<farmtags-filter>] +[subfilter<books-filter>]
Coincidently from a technical perspective, this is related to Is there a way to display a tab, in sidebar tabs, only if a condition if met? - #4 by TW_Tones basicaly which is to allow “inclulsions or exclusions” to the result of a filter.