The ability to select multiple rows in a view or sub-grid by clicking, and then pressing shift and clicking further down to select the ones between.

This was a feature in the legacy interface and has been a feature in Windows and other Microsoft products for decades, so it's a little frustrating that it hasn't been implemented in the unified interface, despite it being out for years at this point.

The only way around it is to click every single row that you want to select! Or select every row and then un-select the ones you don't need. Please look into implementing this.