AndrewF

For anyone else trying to find this, the solution is to right click on the layer and use the "Create Spare Channel" and then later to use "Load to ..." on the right click menu for the spare layer.

Something I'm struggling with in Affinity is that I can't figure out how to copy and then paste the contents of one channel to another. Specifically I'm trying tocopy the contents of the RGB Red channel and then use it to replace the contents of the LAB Lightness channel. In PS or Gimp this would be trivial. Just select the channel, copy, change color mode, select the channel, paste. I've gotten as far as figuring how how to select the channel contents. I can create a new layer with them if I want for example. However I can't figure out how to replace the contents of one channel with either layer or selection. I feel like I'm just going about this wrong and that affinity has a different way of handling this. How does one do this in the affinity way?