This is an example of how to add custom "drop-down," "radio button," and "checkbox" items to Shopify's contact form. This is how to edit them from the theme editor without modifying the liquid file.
Example of adding "dropdown", "radio button", and "checkbox" items to the contact form of the Shopify theme "Rise/Dawn" (changes are made from the theme editor without directly modifying the liquid file)

[(For the Rise/Dawn theme) How to set it up] Add a custom Liquid section to the contact template and insert the code

[Reference] Body of the email sent

