Hi Maurin,
as a work-around you could
1. place those fields in a custom BO.
2. Use the UUID of your XBO as alternative key for the custom BO, thus you can connect XBO and custom BO.
3. Then use an EC of that custom BO with the fields you want to display and place this EC in the sceens of the XBO.
4. Use the UUID for binding the EC to the standard screens. Of course you should make sure that the standard screens hold the anchors to include ECs and that they have the UUID available as parameter for binding the EC.
Hope that helps,
Uwe