Create [custom] fields quickly by navigating to SETTINGS > Coding.
Scroll down to the Fields box and click "Create New".
Name your custom field as you like, select the input type, and hit "Create".
You can create as many fields as you need for your database.
How to promote an existing field to be a Hot Field
If you have certain coding fields that you will be working with extensively, you can customize your coding template to promote those particular fields as "Hot". Your chosen fields will be promoted to the Coding Fields/This Document section in Review and the Hot Coding Fields section in Prep where they will be more readily available for coding.
At the top of the main navigation in Review go to SETTINGS > Coding and scroll down to the Hot Fields section. If you are in a Prep Database, Hot Fields are located under More > SETTINGS > Documents.
You can click "Add New" to add/designate one of your Custom Fields as a "Hot Field" and also Reorder the way the Hot Fields will appear in your coding panel.
If adding new fields to your Hot field list, click "Add" by fields you would like to promote in the Hot Fields section, then click "Done".