Something has to be done to allow adding custom fields and retain data if you change the sort order.

I want add a new value between these and keep the Not Applicable at the end WITHOUT affecting existing values.

Hit add another, drag and drop between, done?

Read the light grey text at the bottom.

In what part of the community are those custom fields? In pages I don't see that grey message.

anywere you can add custom fields with a select box

Not sure why they're drag-and-drop if it can't be altered without affecting the existing input.

11 hours ago, Ocean West said:

anywere you can add custom fields with a select box

That's wrong.... you're talking about the 3rd party application  "Template System", in the IPS core you can move the fields around. 

You should ask the developer of that product for support in her support topic....