Hi @willem_selten ,
So sorry for any inconvenience about this! We will keep you be posted once we have some progress about this.
Currently for "lose the layout belonging to the design block", I have another workaround which should help.
Do you mind to have a try when you have time?
I am very sorry that it needs few extra steps in Fusion..., hope it helps you a little in Fusion 360.
Scenario #1:
If you want to create a new Electronics design to reuse the design block in Fusion:
(Please do the same steps as below, need to handle the board file firstly and then schematic file later separately, and need to make sure that each time only board file or schematic file is opened in Fusion when do paste.)
1. New Electronics design in Fusion
2. New schematic file > Push to 2D PCB > Save all files > Close all files
3. Open saved board file from Fusion data panel
4. In EAGLE > New board file > Add design block for the board file > Copy all from EAGLE

5. In Fusion > Paste all copied from EAGLE in Fusion board file opened in step #3 above > Save board file in Fusion > close board file

7. In EAGLE > Close board file > New schematic file > Add the corresponded design block for the schematic file > Copy all from EAGLE

8. In Fusion > Open saved schematic file from Fusion data panel > Paste all copied from EAGLE in Fusion schematic file > Save schematic file in Fusion > close schematic file

9. In Fusion Data Panel > Open Electronics design > Load the latest version of the schematic file and board file when pop up dialog show up > Save the Electronics design file
10. You should see the schematic and board file are synced with expected board layout too.

Scenario #2:
If you have existing saved Electronics design which has linked schematic file and board file in Fusion:
You could just use step #3 to step #10 mentioned in above scenario #1, should be OK too.
Hope it helps a little bit.
Regards,
Helen
Helen Chen
Principle QA for Fusion 360 Electronics