I added a CM custom macro for this, but it would be great if I could select a preferred Soulbind for each Covenant and have CM automatically activate that one when I switch.

/run soulbindID = 18; if C_Soulbinds.CanActivateSoulbind(soulbindID) then C_Soulbinds.ActivateSoulbind(soulbindID) end

I had planned to add this feature, but there is already an addon for the same feature.
Maybe you can try this.