Microsoft OneDrive does not backup folders outside of OneDrive folder. In order to backup Minecraft game folders, try to create a symbolic link.
mklink /j C:\Users\<userName>\OneDrive\com.mojing C:\Users\<userName>\AppData\Local\Packages\Microsoft.MinecraftUWP_8wekyb3d8bbwe\LocalState\games\com.mojang
/J will create a directory junction.
If there is an error, "Cannot create a file when that file already exists" then it means the first folder parameter/reference already existed. Try to change to a different name.