This article will help you

https://support.mozilla.org/en-US/kb/addressing-email?esab=a&s=add+email+address+in+list+&r=0&as=s

regards, Gautam sharma.

Thank you but don't know how this could solve my problem.

have you gone through the article.??

I think so. What exactly do you think I should do?

Maybe you didn't understand what I need. For example. I want to add you as a part of some user list, name FIREFOX. I do know how to add you, but after I do that, you show both in my personal address book, and in that list, along with list itself. I want you to show ONLY in that particular list, and NOT in my personal address book, too.

All contacts in a list must exist in the address book the list is created in. That is how it works.

So basically I can not do what I want?

That is correct.

Ok, thank you.

How about clicking Chosen Solution to close your thread?

I don't think this is solution. It's more like a explanation that there is no solution.

You are correct. That is how Thunderbird works. Not everything works like we want. Keeping your thread open is not going to change that.