Please add an optional feature of showing the number of tabs in each workspace, so I know how many I still have to read and close.

Nice, but I´d like to choose which tabs go in each group (personalize). Is there any other extension that does this?

@maxgasse Try the "Tab Scissors" extension.
This extension splits a window into two at the selected tab. Maybe this will help you.

Please add an optional feature of showing the number of tabs in each workspace, so I know how many I still have to read and close.

Nice, but I´d like to choose which tabs go in each group (personalize). Is there any other extension that does this?

I have the same problem. Any link (like an facebook email with a button to see a post), lags the mouse. It doesn´t need to be an ad.