Hi @C_R_CT, sorry if my message confused you! Yes, I meant that sub-subtasks cannot be added to projects (multi-homed) via rules, but they can be created via rules indeed.
I believe the behavior is similar to inherited custom fields, which only apply automatically to first level subtasks due to the close connection. If the Developers have any additional information about this, I’ll be sure to share.
@Kathryn_Leigh, I’m sorry to hear that you are also having issues with rules. I’d recommend reaching out to our Support team so that they can look into the logs and confirm if it’s related to the bug they are currently fixing, or if there’s any other problem causing this inconsistency.