The single select dropdown custom field enables you to structure your data inside of Wealthbox; when entering data you can choose from a list of options that you customize in Settings > Customizations > Custom Fields.
To create a single-select dropdown custom field:
Go to three dots in the upper right corner of Wealthbox
Select "Custom Fields"
Choose "Create Custom Field"
Choose the field you are creating the custom field for (Contacts, Opportunities, Projects, Tasks, Events, Investment Accounts)
Select "Single Select Dropdown" for field type
Enter the "Field label"
Choose the "Field options"
Click "Save Custom Field"
An example of this field is as follows: