I have several sieve filters, and it can be difficult to figure out what's working or not other than to see if the desired result occurred. This processing can be slow, and it can be difficult to distinguish between something not working and something not having happened yet.

I would like the ability to show test what a sieve filter would match.

Gmail's filters are able to easily do this because its search and filter languages are the same. Protonmail's is not. Perhaps they should be unified so we could test filter conditionals based on the sieve query language?