Yes, you can add the biller as Favourite via 'Settings' > 'Account' > 'Favourites' > '+' > 'Bills' > 'JomPAY'.
Alternatively, you can also add a Favourite when you're paying a JomPAY biller by toggling on 'Add to Favourites'.
While you're adding your Favourites, you can also set them as a Quick Link which pins them to your Home screen.
Quick Links are eligible for Quick Pay, an additional feature that lets you make payment after you've logged into the RHB Mobile Banking App.