I've never heard of a way to do #1 through Site Admin.
#2 - I don't know how to add a new tab next to the Details tab, but you can use the PageNo property for a field to assign a field to display on another tab that will display in the same area as the Description and Comment tabs. If you search this forum for PageNo you'll find some examples of its use wrt Requirements.
#2 - I don't know how to add a new tab next to the Details tab, but you can use the PageNo property for a field to assign a field to display on another tab that will display in the same area as the Description and Comment tabs. If you search this forum for PageNo you'll find some examples of its use wrt Requirements.