Hide category string in org-agenda-prefix-format for a particular category/filename

Question

My current org-agenda-prefix-format looks like this:

(setq org-agenda-prefix-format
      '((agenda . "%?-2 i%12:c  %?-12 t%?12 s  ")
        (todo .   "%?-2 i%-12:c")
        (tags .   "%?-2 i%-12:c")
        (search . "%?-2 i%-12:c")))

This shows the entries in my agenda like this:

                08:20 ╌╌╌╌╌   ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
   work-notes:  08:30-09:00   Something important
                08:40 ╌╌╌╌╌   ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
      hide-me:  09:00-13:00   I will see this every day
                09:20 ╌╌╌╌╌   ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

There is a particular file in my org-agenda-files list, let's say hide-me.org, for which I would like not to see any information about its category (what is at the left of the time column). It should look like this:

                08:20 ╌╌╌╌╌   ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
   work-notes:  08:30-09:00   Something important
                08:40 ╌╌╌╌╌   ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
                09:00-13:00   I will see this every day
                09:20 ╌╌╌╌╌   ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

Basically, I would like %c not to default to the filename if some condition is met, ideally some property I could set in the org-file itself. Is there any way of doing so? I am getting started with org-agenda, and elisp in general, so if the answer involves some code, I would appreciate a step by step explanation so I could learn.

• I thought on leaving the :CATEGORY: property of the file empty, but it still defaults to the filename

:PROPERTIES:
:CATEGORY:
:END:

• I thought about using (if test then else) in the org-agenda-prefix-format variable, but it seems not to make much sense, due to that being a simple string, so I have no way to get the filename to decide on it.

• Also checked turn-off visibility of category, but that seems to be an "all-or-nothing" approach.

Answer 1

The simplest thing I think is to add an empty #+CATEGORY: definition in the file(s) whose category you want to ignore:

#+CATEGORY:

* TODO bar1
SCHEDULED: <2022-03-27>

would produce an agenda like this:

Sunday     27 March 2022
        foo:  Scheduled:    TODO foo1
              Scheduled:    TODO bar1