Custom contact fields
From Planfix
There are two ways to create custom contact fields: In the Account management – Custom fields – Contact fields:
By clicking the New field button:
When you create a field, you can immediately select the set in which it is to be created:
After the field has been created, it is displayed in the contact templates as follows:
Please note:
If the field was created at an earlier point, it will be in the list of fields that can be found on the left-hand side of the form. You don't need to create the field again: you can create a field once and use it multiple times, in any contact template where it's relevant.