Drag and drop in stye manager isn't how it is done. To copy an individual
style or definition right-click the style or definition, and click Copy.
Right-click the drawing into which you want to paste the style(s), and click
Paste. The styles or definitions are pasted into the selected drawing. If
the drawing already contains a style with the same name, the duplicate name
is displayed in the Import/Export so resolve duplicate style names, if
prompted.