Can I leave fields blank for later office use?

I think you are asking about the required fields. If the form has the required fields, the form will not allow submitting the form without the filling these required fields. On the other hand, you can submit the form without filling the unrequired fields.

If you are asking about anything else, please share more information.

I apologize the thought wasn't complete. I would like to have some fields available to ONLY office staff once the form is submitted, "for office use only". I would like a space for them to write notes in later, but that space to not be available to the applicant.

You can set the long text entry field as read-only. The applicants will not be able to change this field. Please look at these steps.
1. Add a Long Text Entry field into the form.
2. Go to the advanced tab and enable the read-only option.Please contact us if you need further support.

Awesome! Thanks for the help.