Launch the Symbol Editor.
Pick a card, any card… Er, pick a symbol and left click in the left pane.
Right click over the highlight symbol.
Left click “Save a Copy As…” menu item.
In the New Window, left click a new library as the Save destination.
Left click the “Save” button; take note of the following step before actually clicking.
Notice that the “Save all changes” main menu item (second one from left) has toggled from greyed out, to enabled, to greyed out again.
Left click the Close Window “X” in the upper right hand corner of the window.
Note the message “Save changes to “library” before closing?”
I did not actually take note if the selected library gets updated.