If you use Evernote and just want to find your highlights, one method I use is this; it hinges on the fact that Evernote processes images so that the text in them becomes searchable.
Enable screenshots on your Kobo by adding this to \.kobo\Kobo eReader.conf
Code:
[FeatureSettings]
Screenshots=true
Henceforth a short press of the power button will take a screenshot (and a long press will power off).
Take screenshots of the screens with your highlighted text (or just of any screen you want to search later).
Offload the screenshots from your Kobo into an Evernote autosync folder.
Set up (one time) search on Evernote with these parameters and make it a "Saved Search" for easy use later:
Code:
matching ALL of the following:
contains words starting with: screen_
containing: image/png
with advanced filters: intitle:png