Cannot find how to do a simple replace with contents of a tag

Hello, New to MP3Tag - my first few hours with it - apologies if this is simple, but for the life of me could not find how to do the following:

In the title tag, I want to rename the string '25 (XXXX' to using the track number so it would look like '25 - 1.- XXXX' instead, I get LITERALLY the rename string, as in '25 - %track%.-'

It sounds to me that it should be simple, but not only could figure it out on my own, a search in this forum did not return that specific info. A lot of very sophisticated stuff, but for the life of me could not find how to do that simple thing.

I tried using the functions in actions groups and ended up with the same result, that is, a LITERAL '%track%' in the string.

Apologies if this is simple and easy to find, but I just could not. Had to resort to do it manually, just not to go to bed frustrated.

Thanks in advance

If you want to add the contents of another tag field or the contents of a scripting function, you have to use an action of the type "Format tag field" or Convert>Tag-Tag
For a more substantial help please show use the contents of the original field, of fields whose contents should be added.

Ah ! so replace is not designed to use the contents of another tag? I did look into 'Format Tag Field' but while it look it might work or could be used, after reading what it did, doing a quick mental calculation, felt it would complicate that simple task a lot, hence my mind did not accept the solution. In my mind, Replace is the perfect tool for that simple task.

I also was biased due to my previous use of Puddletag, which could do that. Not putting down MP3Tag, of course - it is so good that it convinced me it was better than the free alternatives, it is just that it works different than my expectation.

To answer your request, the contents of the title tag I want to change are:

'Piano Concerto In D Flat Major Op. 25 (Allegro Con Brio)'

This is the first track. I want to turn it into

'Piano Concerto In D Flat Major Op. 25 - 1.- Allegro Con Brio'

Got rid of the trailing parenthesis easy. Doin the Replace as specified in my OP, I ended up with:

'Piano Concerto In D Flat Major Op. 25 - %track%.- Allegro Con Brio'

Again, using the Replace function.

Thanks in advance

... means there is a part in front of the 25 and part following it and there, the track number should be inserted
Try
Format string: $regexp(%title%(.*) 25(.*),$1 25. - %track%.$2)