If you want to program a simulation event in SPAD.neXt but are not sure which one is the correct one, there are several approaches to achieve this.
You can just do try-and-error by programming an event that "sounds" good and give it a try. If it does what you want, you are done, if not, you try the next one.
This is good for common events, where the name is meaningfull e.g. "NEXT_VIEW" to cycle to the next view defined in the aircraft.
However there are events that are well hidden in the system (by either FSX or P3D).
Let's assume you want to bind "open/close GPS window" to a button. If you now browse through the events that have GPS in the name, you will not find one that might open/close the GPS window. If you try-and-error them all, you will notice none of those events does what you want.
How to find the correct event now?
Here one of the (free) add-ons comes into play: The Event Monitor
In SPAD.neXt click on "addons" -> "Event Monitor"
Now you click on "Start" to start the event monitoring. If you want to have the event monitor in a seprate window, just click on "undock" to undock the window.
Depending on what you do right now, it might be the events start to run through the window right now, having a lot stuff you do not need.
You can click on the "Delete" icon next to an event, to ignore this event in the monitor. (This will be active until you restart SPAD.neXt or press the "clear" button).
if you haven't done so already, in FSX assign the function you want to program to a keyboard control.
Press the key that is bound in FSX/P3D to the function.
In our case (opening the GPS window) is usally bound to one of the instrument panels. In most cases the 3rd one (aka Shift-3).
If you press it the event will show up in the event monitor:
Violá, there it is , "PANEL_3" is the event we need. (Note that it appears 2 times, because I opened and closed the GPS Window using the Shift-3 Key)
We can stop the event monitor again (press "stop" button) to save CPU.
Please note, that the event monitor will continue running in background eating CPU and memory if you do not stop it again.