The title shows my request.
How can I get a specified toolbar to open automatically whenever a file collection opens?
I can do it with buttons or context menus but I would like it to be automatic rather than having to remember to do an additional action..
If it's just a couple of extra buttons you want, you could make them appear on an existing toolbar using @ifpath.
For a whole toolbar, it should be possible via Preferences / Folders / Folder Formats, creating a wildcard path format matching
coll://* and then specifying the toolbar on the Options tab.
(Note that the toolbar option isn't available on the actual "Folder Type Formats > Collection" format, but it's available on wildcard/path formats.)
Creating a wildcard path format matching
coll://* worked perfectly. Thank you.