OK, I’m getting somewhere. I added ‘off’ as the default for mode using DDF and now I have cool mode!! Awesome.
{"config":{"battery":80,"coolsetpoint":1300,"fanmode":"auto","heatsetpoint":2600,"locked":false,"mode":"off","offset":0,"on":true,"reachable":true},"ep":1,"etag":"1578b811bb0947f2e040a487b1847839","lastannounced":null,"lastseen":"2022-05-02T22:06Z","manufacturername":"CentraLite","modelid":"3157100-E","name":"Thermostat David","state":{"lastupdated":"2022-05-02T22:05:27.391","on":false,"temperature":1828},"type":"ZHAThermostat","uniqueid":"00:0d:6f:00:05:5b:7e:a2-01-0201"}
I can now set cool/heat in HA and have that reflected on the panel but the reverse does not happen. If I change the mode on the panel, this is not updated in HA. Prior to messing with the DDF, the setpoint was the only thing that was working but like @lgbrownjr, this has now stopped.