The path issue with the REST API Browser has been resolved! Version 63.2.3 fixes the problem.

Again we can take advantage of the feature that makes the API documentation available in Confluence!

...

It appears that this version of the REST API Browser (still) does not cover the latest version of Confluence. Therefore you probably need to download the latest artifact of the app from the Version History page and install it manually. We recommend to test your use cases prior to installing! We already ran the 63.2.2 on a more recent version of Confluence and encountered no problems with that or the latest version of the app so far.

...