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The default settings are to allow internal users to edit this field and external users to only view it. If you do not want external users to see the field, you will need to tick the radial for Hidden next to "Enable for external users".
Additionally, you can give editing permissions as well to external users in instances where you want them to be able to update the information. Internal users may also view only, view and edit, or have the custom field hidden as well.
For the mobile number, we will be using the default settings. In this scenario, the number will have to be entered on the project by an internal user during project creation or on an existing project. Certain field such as those you might add for orders could require external user editing. For example, if they need to attach a company reference number for financial purposes, then the field would need to be at least viewable to external users. (check)viewing and editing.
Complete Field Creation
An additional option resides below these settings and consists of a Custom Field ID. This ID may be used to export the date to an invoice, quote template, etc. When finished, click on OK to save the configuration.
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