This mod gives you a 18 slot hot bar. By default this is rendered as two rows of 9, but can be changed in the config to be 1 row of 18. The upper slot is taken from your top row of inventory items.
There are 3 ways to select an item in the 9 new slots:
Dual Hotbar mode:

Single Hotbar mode:

Here's where the items go to get in the new slots:

No files available for download.