Import tags from text file

There is no specification required. MP3tag uses its internal variables and maps them to the target format. You only have to stick to the field names.

E.g. see this mapping table in the help:

The list does not include RIFF or Wave Chunk?

True. You just have to trust MP3tag and the developer for the time being.
Actually, I suggested with a personal message to update the table in the help.
I found this mapping table on a different page:

That's exactly the same metadata I'm trying to include for BSI Simian Pro! I don't seem to be able to use extended tags to populate any of the Wave Chunk metadata. For example: INFO,ISRF refers to Intro Time (in msec) The other elusive metadata tag is DISP which refers to Title/Description in BSI. For some reason BSI does not use the Title tag.