On Windows 10 if you right click on your taskbar and tick Show Task View button it enables Task Views icon on bottom left, next to Start button.
With that you can arrange your open programs to show in different task view, by default there's three of them.
How do you select in which Task View to load startup programs you have in your Task Scheduler?
E.g. I want to startup Mozilla Firefox on Task View 1, but Thunderbird in Task View 2 on Windows system boot?
Best Answer
You can't specify which virtual desktop programs open on by default in Windows 10 but you could use a third party application like vdesk
For your example you could write a batch file
Running this batch file will open the specified programs on the virtual desktop you define.
You could schedule this batch file to run at logon using task scheduler or add it to one of the various startup locations as described in the link.