@encompass Your best bet would be to pay for the CMS add-on and use a HubDB table to categorize your Landing Pages and build a module that queries the HubDB table and filters on a column value (tag). To my knowledge you won’t be able to use HubL by itself in what you’re trying to do.
HubL is a templating language and doesn’t have direct access to the underlying database structure HubSpot portals sit on top of. Thats kind of why they created HubDB - for people who needed more dynamic/structured content on a page-by-page basis.
@derekcavaliero has the best solution, and using a HubDB table would allow you to store other assets and information with the landing page link and topic so customization options are endless.
If you don’t have HubDB in your portal, would suggest a global custom module. You would need to manually gather and organize the landing page links by “topic”, and create a series of simple menus, one for each “topic”. You could then create a choice field, th value of which would determine which menu shows on the post’s page. Unforutanely site pages and landing pages do not have topics and cannot be access through an aggregate variable like blog posts.