For testing purposes, I need some executable files from different m68k-based platforms. One of these is the X68000, which like most old disk-based systems, mostly has downloads available as disk images in some obscure format. There's a range of recommended ways of working with X68000 ".dim" images, but unfortunately I wasted 10 minutes on them before stumbling on this better way.
The first step is to download Virtual Floppy Image Converter. Then simply run it, decide whether you wish to use it in Japanese or English. At that point, it is rather straightforward.
Change the FORMAT "BKDSK FORMAT" setting to "FILE EXTRACT".
Simply drag the ".dim" disk image into the text area below, which instructs you to do as much. You'll see a sub-directory get created in the same directory the disk image came from.
Apparently some of these games came with source code.
This was pretty painless as far as these sorts of technical tasks go, thanks to Virtual Floppy Disk Converter.