Im completely stuck in Windows

I had Boot Camp installed on my 2017 iMac just a few weeks ago and had the same issue. In the moment I ended up reformatting the disk because I was on a very limited amount of time to complete some work, and I didn't have anything but Boot Camp installed on the disk I was using. Later I found if you boot into recovery mode with Command (⌘)-R you can select System Preferences > Startup Disk and set the disk to the drive you have Mac OS installed on. You will have to do this anytime you want to boot back into Windows or Mac OS. Hopefully the issue of, why holding option is not opening the Startup Manager, is solved soon. Even without a Boot Camp installation of Windows 10 installed on any disk I have not been able to open the Startup Manager by holding option. I don't use any form of wireless keyboard so I can rule that out as an issue.

See About macOS Recovery - Apple Support for reference.

Try restarting windows from the power selection when you hit the windows button bottom left.

As the computer re-boots press and hold Command+R. That should take you through to what is described above.

You have to make sure you press Command+R the moment the computer powers down. Once it starts booting it can be too late.

On restart you hold Command+R once loaded into Recovery click on the apple logo at the top left of your screen, go to System Preferences, and then to Startup Disk. From this menu you should be able to select the proper boot drive to return to Mac OS.