You may want to dispense multiple pairs for a patient but group them within a single dispense. 

Alternatively a patient may have come back in for a reglaze or remake and you want to be able to use the existing dispensing details instead of entering everything from scratch.

All of these options can be accessed by right-clicking the dispense sub-heading on the left hand side of the screen. In this example that is the heading with the caption 

"23/03/2022- 11:55 (Single Vision - Distance)"

Right clicking on this sub heading will expand the menu pictured below and from here you can create a new pair, copy an existing one or perform a remake/reglaze. Unconfirmed dispenses can also be deleted from this menu

If you add a new pair, this will add a subheading to your existing dispense. This can be seen in the picture below, you can then click on the different subheadings to switch between pairs.