Cartwall load list <empty>

[gerritk]

In the cartwall I see empty buttons next to the fade out button.
The empty button can be replaced by (example) JINGLES and will load the jingles.
But how to do this? I can't find it in the manual. And simply pull a JINGLES libary to the empty button doesn't work.
Right click mouse gives noting.

[radio42]

When you hoover with your mouse over the <Empty> button, a tool should/will be displayed:

Ctrl+Click: Assigns the current (selected) cartwall library to this button.
Alt+Click: Clears this button (making it <Empty> again).