I have a font with different styles ready in a folder (within FontBase-Root) and now I want to drag them within FontBase into a collection. If I want to do this, I would have to drag every single (!?) font into the folder. Is that correct? Or is there a better way (there should be …)
Thank you for your post @hm-zrh 
Absolutely no need to do this. Just open the font’s Family page, e.g. by double left clicking the desired font family in the main font list, then selecting the specific font styles you’re interested in and dragging them over to your collection of choice.
Thank you again,