I was asked if there is some software for a PC for reading ebooks (in epub format) and take notes in them. If I have ever to browse an ebook on a PC I use the reader in Calibre which does not offer this functionality, so I am at a loss. Which readers do exist which save notes? Being able to use them elsewhere is a plus, of course.
You can read books and add notes with Microsoft Edge. However, you can't export them.
If the EPUB is DRM free, you can upload it to your Google Play Books account. Then if you enable note syncing from the mobile app, it'll save the notes in a doc on your Google Drive and use that to sync them across devices. The notes will show up in the web reader too, and changes you make on the web will show up on your other devices. Google has instructions for syncing notes here: https://support.google.com/googleplay/answer/6209737?hl=en