Hi,
I have a 4G LTE modem which offers WiFi hotspot. I plan to put the modem near window, and configure connection between the route and the modem via a wireless link.

Is it possible to add a USB WiFi dongle adapter to the router?
Hi,
I have a 4G LTE modem which offers WiFi hotspot. I plan to put the modem near window, and configure connection between the route and the modem via a wireless link.

Is it possible to add a USB WiFi dongle adapter to the router?
No. There used to be limited support for some usb wifi adapters in old RouterOS, but it was removed.
USB-wifi adapters are not supported since RouterOS v6.
But for not much money you could connect mAP or a mAP Lite to one of the ethernet ports on your router.
You could then: