There is a "System Reference Guide" which you find from Creator's help menu. This explains some of the functions.
Additionally right clicking on the Start() function (rather: any function call) brings up a menu that will lead you to the declaration or definition of that function.
Thanks Bob, that right-click thing is faster than GREP. But at a higher conceptual level, what would lead me to understand that a WDT_Start() function is needed when the Global Signal Reference datasheet doesn't mention that it's needed? And what would lead me to understand that the WDT_Start() function needs any of the function that it calls?
The PSoC Creator System Reference Guide (SRG) provides information about watchdog timers but doesn't tie them to the Global Signal component. So maybe a cross reference to the appropriate watchdog timer sections in the SRG can be added to the Global Signal Reference. Also, I don't see anything that explains what is needed to use the other interrupts properly, so maybe cross references can be added for the others, Combined CTBm, System Performance Controller Interface, etc.
Maybe I'm just extra dense.
"Maybe I'm just extra dense." Probably ;-))