Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.1.0

Dragging contacts to mailing lists as part of a different address book does not longer works.

In "vertical" viewing mode it is possible to drag contacts from one address book to another address book but not longer from an address book to a mailing list in a different address book.

In "horizontal" viewing mode dragging contacts does not work at all.

I assume that all platforms are affected.

Reproducible: Always
Steps to Reproduce:

1. Create a new list in a different address book
2. Try to drag contacts from an address book
   to the new list

Actual result
Contact(s) cannot be dragged to mailing list.

Expected result
Contact(s) should be dragged to mailing list.

The workaround to copy all contacts to the other address book and then to the mailing list is very inconvenient when you have huge address books. After copying to the second address book you have to reselect the relevant contacts and to copy these to the mailing list. When you have lots of contacts this is not practically.

Thanks Stephan, good find! And well-described. Not a dupe afasics. In fact, it's a regression from 91 where this works.
Bug 1779825 covers another drag-to-ML fail.

(In reply to Stephan Slabihoud from comment #0)

In "horizontal" viewing mode dragging contacts does not work at all.

Fixed in Bug 1777913 - will land on release channel soon.

I assume that all platforms are affected.

Me too! :-)

The workaround to copy all contacts to the other address book and then to the mailing list is very inconvenient when you have huge address books.

True. However, pls note that due to the poor legacy mailing list design, any contact which you add to a mailing list in another AB will be duplicated in that AB. Bugs on record, e.g. Bug 75711.

After copying to the second address book you have to reselect the relevant contacts and to copy these to the mailing list. When you have lots of contacts this is not practical.

Indeed.

Screenshot 1: Can't drag contact to mailing list of another AB

This also prevents dragging contacts from All address books into any mailing list except if the mailing list and the source contact already happen to be in the same address book. Such inexplicable implementation-related limitations and inconsistencies cause a lot of user frustration and generate needless traffic on support channels and bugs, e.g. Bug 1782692 comment 11.

Also noticed:
Two address books
Each address book has a mailing list.

Cannot copy a contact from one mailing list to another mailing list in a different address book. Assuming it also auto gets copied into other address book at same time.

Able to drag and drop from one mailing list to another address book, but this moves the contact not copy.
Applies to both horizontal and vertical view.
Support Forum user reports this:
https://support.mozilla.org/en-US/questions/1390519

There is a fix in Betterbird for this:
https://github.com/Betterbird/thunderbird-patches/blob/main/115/bugs/1782397-drag-contact-to-ML-in-different-AB.patch
Maybe this works with Thunderbird 115?

In the meantime I was able to verify that this fixes the bug.

Windows users can patch Thunderbird 102/115 as follows:

1. Make a backup copy of the following file: C:\Program Files (x86)\Mozilla Thunderbird\omni.ja
2. Copy the file to another directory that is writable.
3. Open the file "omni.ja" with 7-zip (it is a ZIP file).
4. Go to the folder .\chrome\messenger\content\messenger\addressbook\
5. Use File->Edit to edit "aboutAddressBook.js"
6. Starting at line 885, comment out the following lines:

// let bookUID = row.dataset.book;
// for (let card of cards) {
// if (card.directoryUID != bookUID) {
// return;
// }
// }

7. File->Save
8. Quit 7-zip
9. Overwrite C:\Program Files (x86)\Mozilla Thunderbird\omni.ja with the modified file.