When editing a WP description or any 'Long text' custom field, the "Macros" dropdown doesn't show in the CKEditor toolbar. Is there a setting somewhere or is this by design?

I would think if it I can add macros to these fields (which I can), I should be able to use the dropdown as well.

Hello Joe,

this is indeed by design. [1]
There are actually more macros available then displayed in the dropdown. For example work package and project attributes. [2]

I would be glad to see your feature request with a user story for e.g. the macro-dropdown in the work package description. Please find here a guide on how to create such a feature request: 

https://www.openproject.org/docs/development/submit-feature-idea/#submit-a-feature-idea

Best,

Alexander

[1] https://www.openproject.org/docs/user-guide/wysiwyg/#rich-text-wysiwyg-editor-in-openproject

[2] https://www.openproject.org/docs/user-guide/wysiwyg/#embedding-of-work-package-attributes-and-project-attributes