chrizoo, your feedback is founded, because there were two misspellings in the Formatstring, which I have corrected in the original post.
As a two-year-old user you might have knowledge about one of Mp3tag's strength, which is the possibility to work with user definable tag fields.
Well, your basic intention is to save data, then delete data.
Doing this you need to store data temporarily in working fields.
Try to understand how Mp3tag handles different tag versions and their priority against each other(APE > ID3v2 > ID3v1). It may help to think of a stack of tags, where the lowest stage is ID3v1, second stage is ID3v2 and on top is APE.
Mp3tag cannot handle two tag versions at the same time in the user's list view (but Winamp can).
There are possibilities covered in the Tools/Options/Tags/Mpeg dialog to read one tag version, but write to the other tag version (my proposal makes use of it).
Therefore I speak from "pulling up" tag field content from ID3v1 tag into ID3v2 tag, of course it is a copying process, and not a moving process.
Afterwards you have copied all the tag field content from the lower ID3v1 level into the current ID3v2 level by creating new tag fields of course, otherwise you would overwrite existing tag fields, you can handle these new fields within the ID3v2 tag level.
Understand that Mp3tag cannot display and work with tag fields from different tag versions at a time.
My proposal works around this caveat.
The advantage is that the data always remains in the file and an export and import is not necessary.
When you are ready with your work, you can remove all tag fields, which are not needed any longer, you might also remove the ID3v1 tag completely.
It has just turned out, that my proposal of copying tag field values from the ID3v1 Tag into the ID3v2 Tag will only work to satisfactory, if one can live with the loss of content from a possibly existing ID3v2 Tag.
In other words, my proposal is only good for fresh files, which carry only an ID3v1 Tag, whose fields should be copied into a new ID3v2 Tag.
Although Mp3tag can be set to not removing a complete Tag structure, it does the removing implicitely when Mp3tag is set to write to a specific Tag structure but did not read this specific Tag structure previously. In this situation Mp3tag behaves as if there is no such Tag structure in the file yet and it will create a new one.
My condolences for all the trouble when trying out my proposal!
I will vow to spread my advices to the world no longer with the sandwich in one hand and the cup of Coffee in the other hand.
Hold me in good memory.