Moving from MP3/Tag Studio to mp3tag - rename files

I am a longtime user of Mp3/Tag Studio, but as it has had no support for years I am having more and more problems on Windows 10. So-- I'm hoping that this program will let me do the things I'm used to without too much confusion. I hope this is the place to ask (probably dumb) questions. I'll start with one. NB, I may well use the wrong terms for the actions, as I have only made one pass through the documentation.

If I have filenames with a number followed by a period and wish to delete the period I used expected/output patterns <Custom1>. <Custom2>.mp3 and <Custom1> <Custom2>.mp3. I saw a mention in the document about "place holders", but there was no description or example that I could find. How would I perform this in mp3tag? (I do know that the delimiters would be percent signs, but I didn't want to write a madeup name between them.)

I'll get to harder example later!

As MP3tag is a tagging program, the filenames are not the primary target.
In fact, the best way would be to get the tag fields filled first and then rename a file with the data from the tag fields.
To get a general impression of MP3tag, see

and then perhaps:

I am actually asking about this page:

I note that there is, indeed, an example of a place holder, but I did not realize it, as it seems to differ in syntax from other items. I assumed, from the rest of the document, that the "variables" in the pattern used the % character as both opening and closing delimiters. So would I be correct using patterns like:
%1. %2 as expected name and %1 %2 as output name?

Yes. Probably.
The function has a preview.

Thank you. Is there a full description of the pattern syntax? I might have missed it, but I did cover most of the documentation.

Which pattern do you mean?
The one to fiddle with the filename only?
That consists only of the %1..%n part.
All the other bits are described in format strings, mappings, scripting, actions.

Okay. I need to wrap my head around the differences between the two programs. Having used the old one for 15 or 20 years it will take a bit to get my fingers to type the differences.

I'm sure I'll be back.