This will cover how to channel pack your textures in an RGBA mask texture.
Channel packed textures are a essential thing to have in game development as it saves texture inputs. This tool allows you to pack all RGBA channels to selected RGBA channel textures.
Input your texture masks into the correctly colored input boxes, you can then select which channel to use from those inputs under the packing settings. Here is a RHA (Roughness)(Height)(Ambient Occlusion) texture packed
Here is another example using a normal map with height as the blue channel. (Note: the normal blue channel would need to be reconstructed in the shader)