BW> Upon strace inspection, it appears that Mystic is looking for
 BW> file_id.diz but not FILE_ID.DIZ when importing (e.g. when choosing
 BW> (E)dit --> (I)mport DIZ from a file listing). Perhaps it should check
 BW> for both?

Thats not quite how it works.  It does not look for FILE_ID.DIZ - what it does changes based on the file and whether or not Mystic can internally handle the archive format (ie ZIP, LZH/LHA, RAR).

It opens the file and does an archive listing to find the .diz or .ans file and then attempts to extract the file name that it finds.

If it cannot find a file by internally looking at its archive data then
Mystic will try to extract "file_id.*" and then search for an .ans file and finally a .diz file.  None of it is upper case.

This allows it to handle all types of file variations in case sensitive systems such as "file_id.diz, FILE_ID.DIZ, File_ID.Diz and so on.

... Youth is glorious, but it isn't a career

--- Mystic BBS v1.12 A47 2021/07/31 (Windows/64)