That frontend appears old, I wouldn't recommend it, there were a lot of changes in chdman ever since. The update switch no longer exists.
It seems that there is not a very big interest in chd anymore, maybe with all the buggy chdman releases and all the problems with corrupted/deleted chds, people are now waiting for someone else to do the job, but if nobody does anything, nothing is gonna happen. :(
CHDMan_FE is not old. It's meant to be used with current versions of CHDMan (available in MAME 0.145u1 and above).
'Update' command no longer exist in CHDMan (current) because 'copy' command replaced it.
CHDMan_FE is limited on what commands to perform. Copy, info and verify is the only thing that works with this frontend. On top of it, CHDMan_FE is buggy when performing recursive sub-directory scanning. Doesn't always pick up sub-folders correctly. AnnaWu
recommended QCHDMan tool
in another thread. A little intimidating, but very powerful. Tried it out on two CHDs so far. Works great. The only thing I haven't figure out is how to mass batch CHDs.