Thanks Gael!

Like probably most of your users, at least recent ones, I'm not going to use GCC. Is there any talk of adding a description field to the app interface?

That first link is useful, but it describes the programmable logic operators, which I already understand. I'm looking for something that explains how to determine the meaning of the input types. For example, I'd like my skimmer to come on when my return pump comes on, after a delay of 5 minutes. Could I control the skimmer with a programmable logic statement: "Pump 1" 'delayed on" "300"? But how do I tell GHL that the outlet connected to my return pump is "Pump 1"? That's the kind of thing I can't find documentation on. What is a "Pump" in the programmable logic lingo? Or when a feed pause (filter) is initiated, does referencing the "filter" in PL evaluate to "true", or "false" while the feed pause is active? That kind of thing.

The second link is out of date I think? It shows "Delayed Off" as being a "Function" on the programmable logic screen. But Delayed Off is now an operator, not a function, in the current implementation.