I received this answer from Charles Nurse but because it was given in the benefactors forum I cannot link to it:

Ok - when developing the ability to add a "new" custom property, we realised at a very late stage in development that our "Language Editors" were not designed to accomodate "new" entries.  They can just modify existing ones.

Therefore - in this initial release of the new modifiable Profile, the following needs to be done manually.

Add a new profile property thru the Manage Profile Properties UI.  You should be able to specify "Regex" in the Regular Expression field (although the Regex only applies in this version to Text properties) and set Visible and Required properties.

Add the following keys to the resx file - Admin/Users/App_LocalResources_Profile.ascx.resx.

ProfileProperties_PropName.Text - Label text
ProfileProperties_PropName.Help - Help text
ProfileProperties_PropName.Required - Required Validation message
ProfileProperties_PropName.Validation - Regex validation message

where PropName is the name you gave the new Property in the UI.