Hey, sorry, I realise this is like, a month ago… but I thought I would be able to help you out! Tasks are actually just IMAP items, just like emails, meetings and notes. The way to collaborate with an IMAPS Tasks list is to share that list with another user - your underlying provider should have guidance on how to do that. Usually the way it works behind the scenes is that a “guest” account is created for the person you want to share with, unless you’re both using the same platform, in which case mailbox access permissions can simply be added. But you don’t need to worry about the specifics, really - the important takeaway from this is that tasks.org is not responsible for sorting it out, it’s down to your caldav provider - usually, your email provider!