I am moving from T-Bird and am trying to replicate distribution lists with some limited success. There are LOTS of them. Can I use the Import/Thunderbird process to limit importing to just the T-bird address book?
Yes, when you choose to import selected folders, you can choose just the address book (contacts).
That worked perfectly but do you reallly have to type in the name of the list? I did that but don’t see any sign of a plus. 
Yes, you type in the name of the list, and then select it from the autofill options presented. You can also insert it by clicking on To then choosing it from Contacts. Once the list is in the recipient field, the + appears as in the screenshot.
That seems to be the problem - no options presented
Contacts are all loaded into “local folders.” Wonder if that’s the problem.
The location of the contacts doesn’t matter.
When you start typing in the name in the To field, what happens?
If you click on the word To, what happens?
I imported contacts from T-bird on the “other” computer. Just noticed that didn’t get shared with “upstairs” computer.
Well, I clicked everything but the “To”
Still missing the T-Bird imported contacts from the other computer. Sorry.
In that case local folders does make a difference as they are not synced with the server. 
Ouch. Best way to fix?
The easiest way is to copy the contacts from the one computer to the other.
Go to Menu > File > Export > Contacts to .vcf files. Choose to save as a single file. Then copy the vcf file to the other computer, and choose Menu > File > Import > Contacts as vCard.
If you plan to regularly use eM Client on two computers, you might want to have the contacts synced between them. To do that you need an online contact account. Most email providers like GMail or Outlook.com offer that. Then as long as the same account is setup on both computers, you will have the same contacts. Just move them from Local Folders to the account’s contact folder.
The direct import from T-bird was great and fast. The vcf folder for import gymnastics have been a bust.
OK, the easy way to do that is when the 2nd computer doesn’t have T-bird, just install it. Here’s the plan https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer
The profile desired on the 1st computer has to be loaded at some convenient spot on the 2nd computer HD.
Just install T-bird fresh, load up the desired profile from the first computer and do the import from the top T-bird (top) option. Select the “contacts” option and let’er rip.