Hi,
The best way to manage an unwieldy number of books and shelves (collections) on your Kobo is to manage both your books and collections using Calibre.
There is a sticky thread in this forum that links to the wiki article on how to do this. The thread is here
https://www.mobileread.com/forums/sho...d.php?t=193184
and the wiki article here:
https://wiki.mobileread.com/wiki/Kobo...nd_Collections