You go to delete a database, and get this msg:
The application (mydb.nsf) is currently open. It will be deleted later.
Silly you; you’ve got it open in designer, and in a few view tabs in the client. Close everything you have related to it in designer, and even click on something else in designer; in the client close all the view tabs, click somewhere blank on the workspace to change focus.
In prior releases of Notes, you could then delete it. You can’t in Notes 8.5x, doesn’t properly recognize that it’s closed. Full restart of client and designer required.