Close PROGRAM=onlast will do as the Help says:
Close the program only if this is the last remaining Lister, otherwise just close the Lister. This command lets you create a unified close/quit command.
,confirm is appended and 2 Listers are open, a button with the command does nothing. My expectation is that the second Lister should still be able to close, and when only 1 Lister remains, the program exit (with confirmation).
If only 1 Lister is open
Close PROGRAM=onlast,confirm works fine.
There were recent related changes to this command in one of the betas.
- Directory Opus v12.23.3 Beta x64 Build 7752 - Windows 10 v20H2 OS Build 19042.870