Enable nm-applet's application indicator support
Application indicators are supported since xfce4-panel 4.16.0. Update panel's systray configuration accordingly:
- show-frame was removed.
https://gitlab.xfce.org/xfce/xfce4-panel/-/commit/d77b3b382dd8724489c9210e15f6865964628ba1 https://gitlab.xfce.org/xfce/xfce4-panel/-/commit/8a9c40600a91efe494126042590aa43b65283dd7
- size-max was renamed to icon-size. Specifying 0 means "Adjust size automatically".
https://gitlab.xfce.org/xfce/xfce4-panel/-/commit/3d12067c08e3230756b8804335e1cfbd7a5f3fe4 https://gitlab.xfce.org/xfce/xfce4-panel/-/commit/37b15df58c737949747d7d0eac9419d690027263
- names-visible was renamed to known-items (application indicator) and known-legacy-items (xembed).
https://gitlab.xfce.org/xfce/xfce4-panel/-/commit/6e5e8f5f6130980a281e227657d8191493edc61b https://gitlab.xfce.org/xfce/xfce4-panel/-/commit/7a0b8c36bc940ab648d37a04ffbfc2b0b90b17ac