Seasons Greeting @andre-l and welcome to the Magix Sound Forge users community. Can you elaborate on exactly what you are attemping to do.., i,e,. dragging an entire file to an exciting timeline or dragging a highlighted section from the same or another timeline. Does SF open new instance? .. any error messages?
Also state what version and build of Sound Forge 15.. AS or Pro and build # ? Read the 'Sticky' at the head for the main Sound Forge forum page.