Adding new master from existing

Trying to add a new master to my font by copying an existing one.I use tha “add” button, but only the regular weight can be copied, regardless of which master is selected/displayed. ie, i choose “add” get a list, including “myfont-extrabold”, i choose it, and i get myfont-regular instead. This happens both from another file, and the same one. I remember being able to do this recently.

Start dragging the master on the right, and while still holding your mouse button, add the Option (=Alt) key, then release the mouse button.

That did the trick, thanks