I like the theory but it took a while to make it work.
When using the layer number Cura seems to start its numbering from the first layer of the print piece and doesn't take into account the raft. Then, when the height is set to layer 1 or 0 the extruder temperature changes on the 2nd layer both times instead of the first.
Using the mm height was better but I still couldn't seem to completely understand what the printer is doing. The print is small, approx. 20mmx20mm, so when setting the temperature change for one layer the extruder doesn't have time to cool down before it starts to heat back up again. When changing the 'behavior' to 'keep value' and setting the layer number to 2 so that the extruder cools down for the last raft layer and the first print layer the temperature only drops to 195 instead of the set 180. I'm don't think I understand what the layer number set at 2 actually represents nor what the text that is displayed on the LCD screen when the set layer height is reached, "printing... ch@ 0.7"?
Ultimately, I have a good print that separates well from the raft by setting the printing temperature to 180 then using the ChangeAtZ (Height - 0.9mm, Behavior - Keep Value and No. Layers - 1) to make the rest of the print 210.
I'm using an Ultimaker 3 with PLA and had some trouble with a print a week ago. At the time I managed to fix my issue of the print not sticking using what you called "squish" (I moved the bed closer and it stuck). I had previously tried the raft but it glued to the piece. Now I am simply experimenting trying to get the raft to work so if there is ever a time in future where I need one then I know what to do. Hopefully, I can just use all your suggestions from above instead because this is proving challenging.
Thank you to both of you for the help 🙂