After adding tables the relations between are not shown under all circumstances. When trying to add the relation again, the previously created one is shown in the fields table.
In addition:
I updated the database and performed a db sync. This did not work as I expected and i decided o start over. I used cached project ("continue with" option) and added the table again. It got a number on the end (table name configpack. First retry: configpack1 was added, second retry configpack2). I also cannot edit this alias. It seems that there is a reference somewhere inside consuming the names of the priorily added table instances.