Pause key
The Pause key is used to pause any running fades on an executor. First press Pause then any key associated with the executor where you need to pause the fade. This will stop the fading where it is.
You can start the fade again by pressing Pause and then the executor or if you need to go back you can press Go- and then the executor.
Advanced functionality
Pressing the 
key together with the Pause key will give you access to the Park command. This can be used to park (or lock) any parameter or fixture.
E.g. you need to park fixture number 1:
+ Pause Fixture 1 Please
This locks all parameters of fixture 1. If you open the DMX view, then you can see the parked fixtures and their DMX channels indicated by a blue background. Also if you have any parked fixtures you'll see a blue parking icon next to the command line on screen 1.
Fixtures or attributes can be unparked using the Unpark command or the combination of the and Go+ key.
E.g. you need to unpark fixture number 1:
+ Go+ Fixture 1 Please
If you want to unpark everything then you can also use the Tools menu. Here you'll find a Unpark all DMX channels button.