keka works great when multiple files are dragged and dropped onto the dock; keka produces a single archive, which, when uncompressed, produces a single folder with all the files. But this only works most of the times. keka seems to have a hard time when one of the files is an already compressed file (i.e. .7z, .dmg, etc.). Sometimes, I like to make an archive (with no compression) of multiple applications, like compressing all installation .dmg's for media-related applications into one archive and all gaming-related applications into another archive. This makes for easier backup.
Anyways, after encountering some weird results, I conducted some quick tests, and here's what I found:
.jpg + .dmg = two individual .7z's, one for each file passed to keka (should be one .7z total)
.dmg + .dmg = one .7z containing only one .dmg that was passed to keka, the other is ignored
.jpg + .dmg + .dmg = two individual .7z's; one containing the .jpg and one containing one .dmg (one .dmg is ignored)