Can't locate directories to transfer to

I’m only offered files by type?

I want to backup my e-book directories (/sdcard/Kindle and /sdcard/Nook) to The MZ app only offers music, picture, video, text and apps??

Is the not really a true backup tool for ‘arbitrary files’?

We will be adding a category of “Other” in a future release that will allow you to back up all other files not already categorized by type.