I have a wifi router set as repeater (GL-AR300M-Lite) for my smartphone hotspot. The hotspot settings (SSID + WPA password) are saved in by the router, however it does not connect automatically to it.
https://openwrt.org/docs/guide-user/network/wifi/faq.wireless provides the following commands to scan for networks:
ifconfig wlan0 down iw phy phy0 interface add scan0 type station ifconfig scan0 up iwlist scan0 scan iw dev scan0 del ifconfig wlan0 up killall -HUP hostapd opkg update opkg install iwinfo iwinfo wlan0 scan
so one possibility would be to run a script periodically. But I am hoping for a more direct solution.