PodNotes supports local files. You can right-click any audio file and click Play with PodNotes.

In the podcast grid, you will see a playlist with a folder icon. This is a playlist consisting of all local files (non-downloaded episodes) you have played with PodNotes.

PodNotes will attempt to treat all local files as podcast episodes. This means all standard features are available, such as timestamps, note creation, and persisting playback time. Any exceptions will be added here.