Right click the shortcut, select Properties and add the following to the beginning of the Target box:
%windir%\system32\cmd.exe /c start /high
As an example, a shortcut to notepad will look like this normally:
%windir%\system32\notepad.exe
Adding the above will make it:
%windir%\system32\cmd.exe /c start /high %windir%\system32\notepad.exe
This should work for most programs. Mind you, Obsidian has multiple processes running, so in Task manager you can go into processes and manually change priority on the highest CPU process as well.
I am usually on Linux now and generally I am trying to strip down my Obsidian as much as possible.