Same issue. 2024 MacBook Pro, M3 running Sonoma 14.2. In the iCloud section I created a new list (not a smart list), which it will only name "untitled list'. It won't allow me to edit it. Edit menu, 'Rename List' greyed out.
In another thread I read that it can only be edited if it has a contact in it. Tried to create one on my MBP, but it wouldn't save in 'untitled list'. Created the test contact on my phone, and I can see the new contact on my MBP, and can edit the contact. But still cannot edit the list in any way (Rename, Delete, etc).
To test it further I also created a list (not a smart list) in the 'On My Mac' section, with a slightly different outcome. It created the 'untitled list' same as before but once I created a new contact, it permitted the list to be Renamed. But no change in the iCloud list section.
Can't believe that booting into safe mode and messing about there is the solution on a brand new M3 MBP with the latest software...
Apple, what gives...?