Hi,

If you open the Tab Editor from the Window Customization window (tenant level), the field group is not displayed (whereas is working when opening in System).
Is only working when you select the field group for the active field.

Steps to reproduce
Add a field in Window Customization > Tab > Field and set a field group.
Save
Open Tab Editor : field group is not shown

nb: I've also notice something strange when saving a field from the TabEditor (content of Name, Description, Help are in the base language).
But difficult to find where error is.

Regards,

Nicolas