Suggestions For Improvement

Filename-Filename Conversion demands indentical structure in the selected filenames. If somewhere in the selected collection there is a deviation in the filename structure the programme halts. Only by scrolling downwards you can find out which filenames has been altered and where the programme halted. That's unnecessarily irritating because it is easily possible to rewrite the programme so all changes are shown immediately and to make the cursor to appear at the file/record where the system halted.

Occasionally MP3tag refuses to make a desired change to avoid two identical filenames. Quite useful. But in case of different Artist or Composer or other relevant differences, identical filenames should be maintained. A provision to indicate in advance which tags to compare before deciding to block identical filenames is required.

Aborting on going actions, immediately followed by Edit-> Undo can result in a muddle of tags. For instance Artist's appeared with Filenames where they don't belong. Fortunately I had recent backups.

Why doesn't Format value action works with:
Field: TITLE Format string: %dummy% %title% ?
By the way, typing in Field: TITLE (or a part) results in TITLESORT. TITLE disappeared in the rollout overview.

Values entered are stored. For instance entered format strings, possibly resulting in long lists in the rollout. How to remove stored values, to maintain a useful overview?

An Action groups deselecting button would be useful. Long lists of action groups reach outside visibility of the window. Individual deselecting is bothersome and overseeing a group in deselecting causes problems.

Storing a combination of action groups in Utils is a nice option. But the order of execution is not stored in Utils. That's a pity. Different combinations of action groups could require a different order of the same composing groups. Now, after changing the order of action groups in the action group windows, problem can arise in execution of Utils.

I will enjoy an action to stop playing. Why? After speedy listening to parts of a mp3 I ad codes to the filename to indentify categories. That proved to be much easier than storing such information in separate tags. I use actions to insert such codes in the filename. That requires stopping playing. More over: certainly it will increase speed of execution to offer the possibility to ad keyboard shortcuts to Actions and Utils.

Agreed. I just was about to suggest a feature request at this, but found your post.

I have this issue and I was just about to think it must be a bug in the program, but when searcing for filenames that doesn't match the filename search/replace "very small script in dialog box that contains %1 %2 etc" THEN I found a couple of files that had another filename structures than all other.

Instead of that the Preview and Ok button just disables, there should at least be some text saying that one or more files doesn't match "Old filename pattern". I wish that all files where filename pattern doesn't match should be selected too. Maybe there should be a button saying "Select all files that doesn't match Old filename pattern".

Without that feature, I beleive the user easily beleives this is caused by a bug in program rather than the fact that some filenames may not match.

Thank God this program does exactly that what I tell it to do. So the GIGO principle applies (Garbage in - garbage out).
You could set a filter first to make sure that only those files that match your settings will be processed.
Then you could invert that filter to find all those which do not match. And then think of a decent way to process them. In my view much better than any kind of automatism.
The "filter first" principle applies also to

Is this an improvement or a question for support?
%dummy% has no specific contents but is only the left-over when evaluating all the other masks.
In this particular case:
Which data should fill %dummy%? As formatting a tag with other values you have to specify the contents. If you want to cut the first word, use the $left or $strstr functions.

Please update to 2.47b which features the title again (and read the FAQs before suggesting this feature)

There are numerous threads that have asked this question before. E.g. look at

I've checked this case and it works as expected.
Having the text "Test" in the tag-field TITLE, the action "Format value" using the Formatstring "%dummy% %title%" will set the tag-field TITLE to the result string " Test".

Notice the introduced leading space character, which indicates, that the pseudo-tag-field %DUMMY% is empty as expected.