In previous versions it was possible to show connections like vlan-connections in the NM-applet, through some advanced configuration which had "Show virtual connections". I'm fine if this is hidden behind something for "advanced" or even only configurable in config-files. I've used vlan-interfaces (for a bridged interface) for quite some time for professional work and need it. I can configure those vlan-connections through the connections-editor but just can't show the status of those connections (or bring them down/up again) using the applet. Doing the same with nmcli works without problems. To what I found it seems to be a hardcoded filter. There was an advanced-option in previous versions (KDE 5 maybe still?).