Working with channels and mix them to create new selections

[nostradamus21b]

In my job I work with PS retouching old book covers. In many case I work with channels and calculations (to mix channels I created).
I wanna to make the same things with AP but I can't:
In PS I do:
1) I copy a channel (example: red and rename it to "red copy").

2) I select the recently created channel, double click and can work on it in grayscale (it appears on the viewport) and I just leave a black and white version.

3) When I finish I copy another channel (example blue channel and rename it to "blue copy").

4) The same process.

5) After finishing the blue copy modifications I open the calculations dialog box.

6) I mix the "red copy" and "blue copy" and I get a new alpha channel

7) I use it to mask a zone in the original image.

How can i do the same thing with AP?
I bought the three Affinity apps and I very happy with them. I'm using the 1.7.1 version.

[firstdefence]

You can create Greyscale layers for each colour from the Channels Panel.

You just right click on each channel, red, green, blue remembering to reselect the image layer each time and you end up with this.

Not sure if this helps but might get you a few steps further.

[R C-R]

9 hours ago, firstdefence said:

You can create Greyscale layers for each colour from the Channels Panel.

A macro will do this quickly & easily. Somewhere on this site, I may have uploaded one that does that but I can't find it now.