I don't know how this bug/issue has been overlooked for so long.

The "Update Contact Field" action doesn't have the ability to update number or monetary fields using merge fields. So if you want to update number fields or monetary fields, you have to hard code a number or monetary amount. You can't even use inbound webhook merge fields to update these items. See screenshot.

The "Create Contact" action does let you update number and monetary fields using merge fields, but that action is only usable when there is no contact present in the workflow. So that action can't even be used in many cases where merge fields are needed to update these data points.

Please fix this asap by adding the ability to use merge fields for all contact field types in the "Update Contact Field" action.