Fixed
⌘, opened a blank window.
The app has no main window — it lives in the menu bar — so its SwiftUI scene was a placeholder holding nothing. macOS does not treat that as inert: it wires the scene to the Settings… menu item and ⌘, regardless, and titles the window "HeadsetCompanion Settings". Pressing ⌘, therefore opened a large empty window carrying the same title as the real Settings panel, with nothing in it and nothing to explain it.
⌘, now opens the actual Settings panel. The menu bar item's own Settings… entry opens that same window rather than a second copy of it, so the two routes can no longer leave you with two windows of the same thing.
Install
Download HeadsetCompanion.dmg below, or let the in-app updater pick this up. The Chrome extension ships as sonora-extension.zip — unzip it and load the folder with Load unpacked.
Full Changelog: v0.5.2...v0.5.3