Can’t switch back to OSX from boot camp

I have installed windows 10 with boot camp on my iMac and I am having difficulty switch back to MacOS

I have tried restarting while holding option and which did not work.

I cannot access the bootcamp manager as it is not on my taskbar and does not appear to be running at all in task manager.

Is there any way to get boot camp manager running or another way to fix this issue?