After installing NickelMenu (instructions here:
https://www.mobileread.com/forums/sh...d.php?t=329525), you have to add the following line
menu_item:main:dropbox:nickel_open:library:dropbox to the configuration file at
KOBOeReader/.adds/nm/config (instructions here:
https://github.com/pgaskin/NickelMen...aster/res/doc; edited config file here, if needed:
https://download.ru/files/EvxWjkom).
This will create a Dropbox button on NickelMenu's main menu. Clicking on it you will reach the configuration page for Dropbox synching (just the one you can see here, on step 2, item 6:
https://help.kobo.com/hc/en-us/artic...a-with-Dropbox).
After configuration and synchronization the same button will lead to the books you have uploaded to your Rakuten Kobo folder on Dropbox.