Add "This mapping loaded" REAPER Source
Add REAPER source option mapped to the opening of the preset it is located in.
Also, an additional REAPER source option mapped to the closing of the preset it is located in.
The description of this issue sounds a bit different than its title. Is this about "Preset loaded" or "Mapping loaded"?
If you want "Mapping loaded", you can achieve that by using the "Timer" source and setting a very high timeout.
I interpret this as "Mapping loaded/activated" for now. The "Timer" source is a workaround. "Mapping loaded" and "Mapping unloaded" source would make sense. They should also trigger when the containing ReaLearn instance gets enabled/disabled.
+1 (I had the same wish in #746)