This is not possible in the limited WinSCP console terminal. Use "Open in PuTTY" command to open a full-featured PuTTY terminal from WinSCP.
See https://winscp.net/eng/docs/integration_putty#open_putty

I am using the WinSCPnet.dll for creating ssh connection in my current project.
When I try to start a linux command as a background process with an ampersand "&" after the command, I always get an error (Connection has been unexpectedly closed. Server sent command exit status 2.) and the connection closes.
After searching the internet and forums I still didn't find a solution.
The error can be reproduced when opening the Console in WinSCP and try "sleep 30 &" (just for example).
When trying the same in putty it works.

Does anyone have a solution or an alternative method for starting linux commands in the background using SSH?

Thanks in advance!