I am still dealing with filtering the collection in the Firebase database. I made some progress and the picker that I have put in placed is working creating several categories and writing in the query field:
My problem is that it doesn’t show any item in the beginning because the dataslot is empty obviously. I have tried to write all values separated by comma in the default value for the slot (“Principiante”,“Muy fácil”,etc.) but it doesn’t work. Also, I would like one selection in the picker that would allow to show the entire collection. I am not able to figure out how to do it.