As of version 2024.1 (released march 4th), they've changed how WADs are managed.
From the github release:
WAD files are now managed by clicking on the wad property of the worldspawn entity. Selecting this property will show a list of WAD files below the entity property table. Use the buttons below the list to manage the wad files.
From the github release:
i recently started on my first map (of any game, let alone half life), so once i'm done with that, this'll be a great project