[Mathias]

A thing is just an entry in the database of potential options for the game - it's just what you entered in the editor, converted into end-use form. In effect, foreach thing is read-only.

What you are asking for is not an option as far as I know, because the tags and fields on the things are fixed, and each table has a fixed sort set.

The closest I can come up with would be to have three (if it's more than that, then skip this) nearly identical tables, differing only in the sort set, and the one that becomes visible is determined by your base pick.

If you're flagging "options X and Y are highly recommended based on your other choice", what we've done in the past is to make use of the thing template for that table - find a way of highlighting those recommended options, with colors, badging icons, or a column that doesn't have any entries, except for those recommended options. An example of this would be the blue color on class skills in d20/PF1.