@mzel. You can apply NiLuJe workaround once, enable hidden files, navigate to .kobo/dropbox and, once in that folder, press the "+" button on the FM and click on "folder shortcut options". Then you can add a new shortcut, long press to select current folder and rename it as "Dropbox". Once the shortcut is created you can hide hidden files again and update normally (changes in internal files will be overriden on ota updates anyway)
I think there's some shortcut to open the folder shortcuts directly but I don't know
