back up your claim please:
rather than say it is TRIVIAL, & then walk away - how about you prove it by giving us the batch code to do what' been suggested i.e. to scan an entire calibre library & place each original_FMT file into its own individual .rar or an 7z container of the same name , in the correct book subfolder.
('cos I don't think it is trivial at all but will be happy to be proved wrong/ to learn how )
What was was suggested will require repeatedly invoking the main RAR or 7z .exe and handing it each found file via command line options?, without losing control of overall flow.
you lose marks if I am left with several hundred instances of RAR /7z still open at end of batch run.
and then write the matching one that reverses all of the above, if you can.
PS for a gold star you also have to do all of the above in less time that it would have taken to teak calibre source file select options in convert screen
