Somehow text in the model view is not displayed in detail.
Tried “show in detail” / no layer is turned off for this detail.
Also not visible if i create a new detail.
I discovered the problem by myself.
I imported text from Rhino 5. In Rhino 6 this text is visible and has a text style (AnnotationStyle 05) and scales in layout!
I deselected layout scaling, now everything is visible.