[nynaevelan]

This is what I did to try to get it to work:

1. set output option for mobi personal tags to Catalog
2. set extra tags in news to Catalog although I do not use the news feature
3. unchecked option to automatically send conversions to kindle
4. reboot Calibre
5. deleted existing catalogs from Calibre and kindle
6. selected and converted to mobi 2 catalog files
7. copied the converted mobi catalogs to kindle
8. rebooted Calibre
9. created a preview of collections on kindle collections plugin

And this is the warnings:

WARNINGS:

These books on the Kindle cannot appear in any collections on the Kindle because the book information is not set correctly. Try reconverting/resending the book. If this is a News feed, check Preferences->Output Options->Mobi output and set "Personal doc tag" to a tag you are using for the news feed, e.g. "News" (To use a tag other than "News", also set the News feed tag: open the specific news feed and add the tag to "Extra tags" under Advanced tab:

Title: How To Geek
Code: #0e220604-dcb7-4513-805d-68abd9a679c1^None

Title: Not Romance On Kindle 031511
Code: #d4f9cae4-3e3a-4647-8afe-316b02bcb20a^None

Title: Romance On Kindle 031511
Code: #8c874181-6088-450e-b1f3-7a4a9b6b3a0b^None

I do not have news in any of the tags so I don't know what is wrong, maybe you are right and this is a limitation of the k2.

EDIT: I do not think it is the plugin, I think there is something about these mobi files because the option to put them into collections is greyed out on the kindle itself.