Action to remove "empty" TCMPs?

My two-way database-filetags import/export process results in all files containing the iTunes compilation flag, most of which are set to empty/NULL (or 0 if that's easier), rather than simply being "absent if not 1" as is widely recommended.

How can an Action be configured to remove all such fields, leaving only those ="1"?

Also (asked elsewhere with no response)

Is there a way to "call" one Action from another?

Or flag an Action as "autorun" to run against all files loaded automatically at startup?

Or launch MP3Tag with a list of actions to run?

Have you tried importing any blank fields yet? Generally speaking, Mp3tag will not save a blank field (although I've encountered a bug or two where it does). You can use a conditional to set a field to a blank, or keep it at its existing value. Setting it to blank should remove it.

Action type: Format value
Format string: $if($neql(%compilation%,1),,%compilation%)

The answer, AFAIK, is 'no' to all of your other question. You can save and recall sets of action groups using the 'Utils' button in the action groups dialog. Not quite the same, but it makes bringing up a known set of actions a two-click process.

Thanks very helpful sample Action there even if MP3Tag ends up not needing it - I'll make sure my import has proper "null" values, maybe an issue with quotes or something.

And I'd missed that "saving sets of Actions" button, very handy thanks (Florian as well of course).