I have used (the Thunderbird Add-on) CategoryManager to put 100 of my contacts in a sub-group. I was hoping to export this group by itself but can't see how. If, as I was imagining would happen, the category appeared when selected as a column for display, I could have exported the whole address book and continued in Excel. But it doesn't. I can display the 100 contacts by themselves and send a message to all of them (possibly useful). I thought that selecting them all and right clicking would allow selective action but no, any action is applied to entire address book. I also tried creating a sub-list. It is rather more laborious than assigning a category but I thought it should surely be possible to export such a thing. However, I found that it was volatile with unpredictable contents (it's latest trick was to disappear entirely!). I also have 'MoreFunctionsForAddressBook' add-on as the name sounded promising and (I think) it claims to offer the feature I am looking for; however, I couldn't make it work for me in that way. If anybody can advise on the best way of exporting a sub-group using these, or any other add-on, I would be extremely grateful. It took me a while to discover how to do this in Windows Live Mail but Microsoft has made it impossible to reinstall WLM after latest Windows10 disaster so I chose Thunderbird as best available alternative. I like many of its features and would like to stick with it if possible.