How to make Windows 10 notifications appear in the top right of the desktop?

Seems it can't be done:

We realize the inconvenience you are experiencing with not able to move the position of Toast notification from bottom to top. We will certainly help you.

https://answers.microsoft.com/en-us/windows/forum/windows_10-start-winpc/how-to-change-toast-notifications-position/98d3efba-dd78-4a53-b4b4-9ba36b28c794

Actually you can do it with some registry modifications. Here's the step to follow:

1. Open the Registry Editor (with the command regedit)
2. Go to following key: Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer
3. Create a new DWORD(32bits) Value called DisplayToastAtBottom and enter 0 as Value data
4. Restart your computer