Sorry, still a little unsure as to where you are referring to seeing this. The mention of "folder" suggests you are looking at the files and directories on the device. If that is the case, the save template you list doesn't produce either what you want, or what you are seeing. Did this come from the driver configuration, or from the "Sending books to devices" page of the preferences? If the latter, you need to look at the driver configuration. The save template on the "Sending books to devices" page is the default, but when you change anything on the driver configuration and save it, this is copied to the configuration and you have to edit it there.
But, if by "folder" you mean a collection on the device, then it should be using the metadata plugboard to set the title of the book. And it doesn't matter whether you look at the book in the collection or the main library list. The details are the same.
If this isn't being set, then either you aren't using the KoboTouchExtended driver (see above to check) or the metadata plugboard is wrong. Looking at your post you have:
Code:
kepub:kobotouchextended =([{series_index:0>2s | | -}{title}
That is not a valid template. The first two characters are "([". There are no ")" or "]" to match these. I assumed these were a typo or cut-and-paste error, but, if they are in the template, it is invalid and the title won't be changed.