In v5.3.8 and earlier filters did not have a problem with fields with parentheses in their names. E.g.,
[regexp:_cd-work(s)[(?i)suite]]
worked flawlessly.
In v5.4.0 this no longer works:
I will be probably be warned against using parentheses, etc. in field names, but as mentioned, this used to work in versions prior to version 5.4.0. Also, according to https://tiddlywiki.com/#TiddlerFields field names may contain any combination of characters.
(Luckily, when I wrote my music player, I also wrote some simple metadata tools for editing (copying, deleting, setting, etc.) fields in (filtered) lists of tiddlers.)
Is it possible that this new behaviour is caused by the addition in v5.4.0 of new syntax, in particular parentheses, for multi-valued variables?