Additionally, while the blocked: true Lucene search field does successfully filter, for the admin one it looks like app_metadata.isAdmin: true which is a bit hard for non-technical users to remember if they need to use it. (with the users we intend to have use this tool, not particularly convinced the first one is going to be particular useful for them either!) The idea is that using the Sort operators to group the records by these values will be a valid workaround.
(Unfortunately, adding the columns to the search dropdown isn’t exactly ideal either, as it prevents global search: you can now only search the column specified. Also, if you want to show say where isAdmin is either false or null, the search criteria is now NOT app_metadata.isAdmin: true; which when the field is a dropdown, you can’t actually enter. To make this work, I had to create a specific userField with the name “NOT app_metadata.isAdmin”, have it hidden across the board, but exposed as a search dropdown. You still had to enter “true” into the search box, however!)