Solved: Bootcamp Windows 10 Bluetooth not functioning
Most of the suggestions like switching setting in windows device manager don't works for me. Turns out, inspired by reddit community, the solution is to turn off bluetooth while you are in macOS, and then restart and switch to Windows OS, the bluetooth works fine with the external wireless device, no more disconnect with your bluetooth keyboard and mouse. Hope this will solve your depressing problem, I've seen a lot of Microsoft and Apple official answer of the topic but not of this solutions help.
MacBook Pro 13″, macOS 10.15