Is there a maximum number of subsubfolders allowed in a subfolder of the Inbox folder? I've added an 11th subsubfolder under a subfolder, but it is not possible to move or copy a message from the inbox into this 11th subsubfolder. Files can be copied and moved from the inbox into the other 10 subsubfolders and from them back to the Inbox. Might there be a limit of 10 functional subsubfolders under every subfolder? Is it possible to increase this limit? I'm running Tbird 68.12.0 (64-bit) on Mac Catalina 15.6. Thanks much.