@mike_i/@booklover6: Yup, you'll need a jailbroken PW with
ixtab's CM installed.
After that, booklover6 pretty much perfectly summarized the workflow (whether you use a custom column or not is irrelevant to the PW-specific situation, I personally don't, and build collections from specific tag prefixes). Note, that, if, like me, you only work on collections in Calibre, it gets a bit easier/faster, as there are settings dedicated to this specific workflow in the
PW friendly tweaked version of this plugin.