For macOS: 1. In Finder, navigate to your vault, and open this folder. I’ll name it “Life’s Work” for this example. 2. Press Command + Shift + . (period) to see hidden files 3. Go to folder `.obsidian > themes` 4. Copy desired theme, Comfort Color Dark for example, and paste (or Option + drag) in or to the vault folder, “Life’s Work.” 5. Rename this file, `Comfort color dark.css` in my example, to `publish.css` 6. Then in Obsidian.app, press/click “Publish changes” in side ribbon. Select `publish.css` from New row, then press Publish. Now your favorite or preferred app theme is also used for Obsidian Publish without knowing or customizing a jot of CSS.