There was an introduced bug in 13.3 which is also in 18.104.22.1682. The Object Palette used to support type ahead filtering on the schema name, the same as can be done in the Schema Browser. Since 13.3, if you click in the Owner dropdown and type a letter to jump to schema names beginning with that letter, it will just flicker and remain on the currently selected schema. Type a few characters and it will flicker for each keystoke. This used to be a very handy feature but now it's a slow task if there are a lot of schemas in the database.