I upgraded from macOS Catalina to Big Sur, which of course brought Safari 14. When I have the Bitwarden extension enabled–and only then–do I experience slowness with opening new Safari windows. There is ~2-3 second delay for new windows to open, but not new tabs. When I disable the Bitwarden extension, the slowness disappears and new windows open instantly.
Has anyone else experienced this, or have a suggested resolution?
Turns out that this is a known issue, which apparently will be fixed with the conversion to WebExtensions API. It sounds as though a release is expected in early March.