Work at the same time on the same project

Hi! it depends on what you mean with dashboard. You can create a workspace for pro users. In there you can collaborate with other pro users. Working in the same report at the same time is not posible in Power Bi. The best practice would be working with the pbix file in a repo one by one to keep the source file consistent. 

On the other hand if you are talking about the "dashboards" content inside a workspace, the one created by pinned visuals from reports, that one can be modify at the same time. I don't think it would be a nice pleace to be moving visuals at the same time, but you can.

I hope that helps,