There is unfortunately no (native) REST API for Obsidian - see this comment from their team on their forum: https://forum.obsidian.md/t/is-there-are-rest-api-available/78627/2

Obsidian is a locally installed desktop application - there is no server component for a REST API to interact with. While it's technically possible to synchronize your Obsidian vault with an external datastore (either Cloud storage or the paid Obsidian sync service) those vault files aren't accessible outside of your local desktop application.

If automated integration with your note-taking app is important to you, we'd suggest looking at switching to an alternative, such as Notion, which does have a Make app.

If you're using Obsidian with the Zettelkasten note-taking system, this Notion template would be helpful: https://www.notion.com/templates/zettelkasten-note-system?srsltid=AfmBOoqqn0TbetE4XmNMoabnagxLkcoy8dEjAD6rqeCe05LhaLufbxPq