In a window accessible by a role, it is possible to define for each of its tabs if they are editable or not through the Editable Tab check.
If the window is editable (Editable Field is checked), by default all its tabs will be editable. But it is possible to define some of them not to be editable for this role by adding them in this tab and setting to false the Editable Tab check. Note this is only true if the table behind the tab is editable for the role.
In the same way, having a non editable window it is possible to define some of its tabs as editable by checking Editable Tab.