hi there, what about using headers on the pages where you want to apply a custom css to your outline? I think you can adapt the Tables example here, to your Outline.
This is how the header (or first lines) of my note called “Weekly” looks:
That header info in YAML style tells Obsidian to apply the cssclass of .whiteRed to the tables on that note.
And the .whiteRed css makes my table look like this:
