Running Sieve Scripts on Proton Mail is rate limited, but creating and testing, maybe debugging new scripts sometimes needs a lot of iterations.
While I do understand the need for such rate limits, it's a significant roadblock for any sort of testing. Thus my request to get debugging/testing features for filter scripts.

For this purpose, there are two features I would like to suggest:
1. The ability to test a filter against a select number of mails from the account, rather than each and every email. It would then list any actions performed on each selected mail, rather than executing those actions. This would make testing faster, reduce the server load for testing filters and increases time till any scripting rate limit is hit.
2. A debugger feature that lets you step through each line of the sieve script, inspect variables, define breakpoints and send debug messages.

I understand that Sieve is probably more a niche feature and that this isn't going to be a top priority to add, but I would really appreciate the first suggestion to be added. The second suggestion is more of a moonshot, considering the time and effort it would take to implement, but it would definitely be a very useful tool to understand why your Sieve Script isn't working the way it's supposed to.