I am using since at least with the start of Plasma 4 to use the window-decoration «B II». This is for me important, that the first line on the very top leaves the free space and runs not until the right edge of the window.
How can I get this back, please?

Why can I not attach a small picture to show exactly what I am looking for?

Did you try searching the store where you can get new decorations? It should be accessible through the same place where you change the window decorations, small button labelled "Get new decorations".

Keep in mind that many of those external decorations are third party made and might not always be available.