In order to add a custom field to a license, you'll need to add the custom field to the category the license is using. That way, it will appear for all licenses using that specific category.

Let's add a custom field to the license below, Final Cut Pro X.

Start by clicking on the category of the license.

Now, click on the Edit button.

Scroll down on the page until you see the Custom Fields section, and click on the Show button. This is where you can add your own custom fields that will appear for all licenses using this category.

These are the types of custom fields you can create:

You can also choose if the custom field should be a required field or not. To add options to a Dropdown List custom field, you just need to fill out the Dropdown List Content field using this format: ["Option 1", "Option 2", "Option 3", ...]

In this example, we've added one custom field; Optimized for M1/M2 (Checkbox).

Once you've added the custom field, scroll down and click on the Save button. Then, go back to the license page and click on Edit License.

After scrolling down to the bottom of the page, we can see that the custom field we added is now visible and can be filled out for the license!

Once we've filled out the custom field and saved, we can see that it now appears for the license!

In order to remove a custom field from a license, you just need to go back to the Custom Fields section of the Edit Category page and make the Field Title field empty for the custom field you'd like to delete, and click Save.