Admin users can now give other users rights to add, edit and delete custom fields
Admin users can navigate to https://app.pipedrive.com/settings/permissions and give other users the right to work on the custom fields settings.
Are you not an Admin user but this would greatly help you in your daily work, ask your Admin user to set it up for you and be sure to learn more about how custom fields work in the Academy.
Depending on the pricing plan your company account is on you can create different groups of users, with different permissions, read more about that in our Knowledge Base right here.
Have fun ⚡