Is it possible to abort an action if an error condition is encountered?

Support
1

I have a large action with many entries. I would like to add an entry (or multiple entries) to the beginning that check for error conditions and abort the action if any are found.
Also, if I run the action on many audio files I would like to know which files caused the abort, either by stopping on the first error item or displaying a list of problem files when complete (like rename does).

For example: If the track number or trackname is empty then I would like to stop the action.

If (expression is false) then abort

Is this possible currently?

2

I do not think so.
It is possible to use scripting functions with conditions, but such an expression would not lead to the termination of the action(s).
The way of operation in MP3tag would be to filter to get a list of files that should be treated.
e.g.

you could get a list of files with no track number:
%track% MISSING
or a list with files that have a track number:
%track% PRESENT
see the help on filters: