10 rules to have a minimalist desktop:

1. Have an expiry period for the tabs on the browser. You must close you all tabs after 3 days so that you don't have any attention residue left. Often when you log in and see the old tabs, it triggers a chain of thoughts that make you believe that some work is pending. 
2. It helps to work in full-screen mode.
3. Use the color coding in Mac properly. ( Like Red for important files, Yellow for books that can you read in future, blue for technical papers )
4. You can also use folders for bookmarks.
5. The dock should only have those files which you use frequently. ( No need to have contacts, maps)
6. Use content blockers/ad blockers always when working on deep tasks.
7. Have nature images as wallpapers.
8. Use the screen time trackers.
9. Excel is also a good tracking tool.  No need to download specific apps for that.
10. Always define the relationship between your device and you. If it is a work computer, don't use it for entertainment.