Q.Peppers
My small plants of Red Pepper are damping off and dying in the unheated greenhouse. Am I keeping them too wet/dry? I water when the (“which” recommended) potting compost looks dry, usually from the top, but sometimes I will stand them in a tray with about 1″ of water in it, if they look
extra dry. This is the third year this has happened. Help!

There's a good chance the greenhouse simply isn't warm enough (this includes the soil). Pepper plants are extremely sensitive to cold. They also like well-drained soil, so standing them in water may not be doing them as much good as you would think.
These articles may help you:
https://www.gardeningknowhow.com/edible/vegetables/pepper/how-to-grow-red-peppers.htm
and
https://www.gardeningknowhow.com/edible/vegetables/pepper/growing-peppers.htm