I'm a software developer, and I think of the application of filter rules as core program in-process tasks. The filter is something user-defined, but the invocation and application of that filter is a task enacted by the actual program. Having the ability to view when a core program task is in-process would be beneficial. For example: if I import email from an unsupported client, that could be viewed as a task in an in-program task manager queue; after importing, if I create a filter to send all mail from joe@schmoe.com to my Trash folder and choose to apply it to my existing email, that would also appear in my list of in-process tasks. An MVP could be to simply see a list of program tasks being performed, and roadmap improvements could include: queueing tasks that cannot happen concurrently, like applying a filter to existing emails; the ability to pause a task from the "task manager"; a log of performed tasks that are not continuous. I don't know your architecture, but it would be nice to have.