Currently, there is no way to overlap sheets on a dashboard or get rid of the frame. However, this might be a good one for the Ideas section!
Thank you for your answer.
It's a pity that I'm not able to change the frame, but what exactly is the "idea section"?
Sounds pretty cool...
The Ideas section is a place where the community can leave their comments and feature requests for our developers to see and for users to vote up or down. It can be found here: