In a teams channel - have whiteboard visible alongside chat - like it is done in Skype For Business
We set up a team - and for each project that team is working on we open a new channel.
When cooperating using Skype for Business we would open a whiteboard in the chat and put agreed upon items on there.
This was always visible for those in the chat, and those invited in could see what had been agreed before they entered.
The channels in Teams does not seem to have this function - things can be added as separate tabs - but that is not easily visible, having to jump between tabs to see if any updates have been made.