When macOS is missing from the Windows Boot Camp Control Panel, macOS is usually installed in a APFS container. Since you did not specify this information, I will make this assumption. Originally, this was a problem when APFS was first introduced, but since then Apple has released updates to Boot Camp to fix this problem. Any such updates can be downloaded by executing "Apple Software Update" from Windows.
Note: If "Apple Software Update" shows an update for "Apple Software Update", you probably should download and install this update first. This may happen more than once.
In the event there is no Boot Camp update available to fix your problem, then you could use the solution that was posted here at Ask Different four years ago. The idea was to add a small partition that Boot Camp installed in Windows would detect as macOS and thus could be selected from the Windows Boot Camp Control Panel or from the right side of the Windows taskbar. You would have to install into this partition and configure a free third party boot manager call rEFInd. The full instructions are given in this answer. The answer probably needs to be updated, but this would possibly require the following information.
- The output from
diskutil list
- The output from
diskutil apfs list
- The version of macOS
- The version of Windows
- The model/year of the Mac