Rated 5 out of 5 stars

Suggestions:
- Automatic contacts search and merge tool (like in Google contacts).
- Integration with Thunderbird's filters - as for now, it doesn't see CardBook's categories and addressbooks.

Implemented features, many thanks:
- Possibility to merge contacts when search filter is used.

This review is for a previous version of the add-on (9.8). 

there already is a merge tool (right click on selected contact(s))

for the yandex categories, may you contact me by email : cardbook.thunderbird@gmail.com