I just updated from 9.7 to 12.6. In 9.7 there was an option to select in Schema Browser \ Data \ User/Schema lists that would limit the drop down list to just schema owners. I have a couple hundred users in the database I have to deal with the most and only 4 schemas, but searching through the drop down is a hastle.
Please let me know where to select this option in 12.6. I think I have found all the other options I generally choose.