Thanks @CawlinTeffid but this did not work out. I deleted the cache DB files, restarted Obsidian, and the CPU load is at 100% again.
Maybe I am wrong about IndexedDB being the source of the high load.
Is there any way to dig deeper into what’s going on inside Electron?
(I am thinking of Chrome’s about://tracing but I don’t know if and how this works with the release version of Obsidian.app)