A few ideas about planet filters, not game changers but would be helpful for me:

1) Make the flagged planet filter AND-stackable with the other filters (e.g. intersection of "Your Planets" and "Flagged Planets", seeing only the planets that match both criteria)
2) make the filter OR-stackable (e.g. union of "Unoccupied Planets" and "Enemy planets", seeing all the planets that match either criteria)
3) add an "Unflagged Planets" filter
4) add the ever-popular flag color filters

I like the idea of the "flag color filter" sounds like something I would find useful