Congrats - this is definitely needed since the Firestore default GUI is so limited. I suggest an FAQ and include the Firestore query quota costs. If someone gets 1 million docs back it will go against their monthly quota.
Thanks! That's a good idea, we'll put info about the numbers of read/write/delete operations that Firefoo uses up somewhere. For long-running tasks (export, delete/rename colls) we show those numbers in the Tasks popup already but it'd be nice to show them up front!