From the patch notes:
"Due to all the balance changes, for a limited time all enchantments and runestones can be traded for other enchantments and runestones of the same rank."
I can see how to exchange Eldritch runestones for Bonding, and how to exchange Enchantments for either Runestones or other Enchants.
However there is no tab for exchanging the other types of Runestone. Is there some other method for this?