Hello,
I just want to give my input where I had tried re-installed latest Sierra QMI drivers as yours for my EM7455 on DELL E7270 running Windows 10 where previously all related devices are shown inside Windows Device Manager BUT as you had mentioned related device(s) under Modem and Ports were missing except under Network and USB. I’ve un-installed that QMI drivers and remove directory “Sierra Wireless Inc” and re-installed that SIERRA QMI Drivers (Build4581) via command line by supply “USBCOMP=8” and that missing related devices under Modem and Ports were resolved.