Maybe I used the replace button on 1 or 2 images, but not on all images and I am pretty sure, that I did not open Publisher within this project.
Nevertheless, the project is in draft mode and I can start from scratch. Now the situation is like this, that every new image is linked and as it is not possible to open the resource manager I cannot change the status to embedded. To continue with this file I must rename one image to force designer to open the resource manager when opening the file. Then I can change to embedded. But this is not a workaround that’s useful.
Just now I installed Designer trial version on a windows 10 machine. I will try something here...
Anyway, it would be very useful to have a resource manager within Designer and to choose the way of placing images in a new document. Often it is nice to work with linked images. Sadly not in my case.