Choose default address book to add contacts to when using the "Add to address book" when you right click an address.
I installed the addon TbSync (https://addons.thunderbird.net/en-US/thunderbird/addon/tbsync/) to sync my address book to my email provider. After installing I added a new address book that is being synchronized. I also set this address book as the default startup directory.
Now when I have an email open and I right click the email address of the sender to add it to my address book, it adds it to my "Personal Address Book". This one is not synchronized and I don't want to add it to this address book, I want it to be added to my Posteo (name of my email provider) address book, which is synchronized.
I also set the option "Automatically add outgoing e-mail addresses to my" (in Preferences -> Composition -> Addressing) to the Posteo address book. But the behavior described above stays the same.
It would be very nice if I could add it directly to my Posteo address book, so that I don't have to move it there or manually put it there.
Opaite Mbohovái (1)
I think the only way to do this is to click the star next to an email address. Click once and it's added to Personal Address Book. Click a second time and Edit Contact appears where you can select the Posteo address book.