Macos – how can I have a persistent group chat on lync

I want to create a group chat just like we can do in Skype. I open a chat to one person, then click on 'invite by name or phone number' and add each user one at a time.

Then we can have a group chat.

But as soon as anyone disconnects, they are removed from the chat – even after they reconnect. So by the end of the day there's only me left. And the next morning I have to recreate the chat session. Eventually I get bored of doing the same thing again and again and stop talking to my team.

We only use Lync in the office since Skype is blocked for security reasons (don't ask).

How can I make a persistent chat session?

Using Lync 14.0.9 for Mac.