You can do this without Steam. Right click the .exe and select create shortcut.. Then, right click the shortcut, hit properties, and add a space, then, after the space, add -force-d3d11 to the end of the Target field.

Ex:
Target: "C:...\Rhythm Doctor.exe" -force-d3d11

Hit OK and launch the game from the shortcut. This is what Steam refers to as a "Launch parameter", IIRC. The other method of accomplishing the same thing would be to create a new text file in the same directory as the executable and open it in Notepad. Write the following in it, then click File > Save as..., select "All files" as the type, and name it "start.bat" without the quotes. (Note: NOT "start.bat.txt") Then double click start.bat to launch. The following is what you'd type in the Notepad:

"Rhythm Doctor.exe" -force-d3d11

Alternatively, instead of a batch script (.bat) you can use a PowerShell script (.ps1). Save it instead as "start.ps1" (without the quotes) and write the following instead:

& '.\Rhythm Doctor.exe' -force-d3d11

Then double click start.ps1to launch.

Finally, as an alternative to the first method using shortcuts, you can (instead of Create shortcut) select Send to > Desktop (create shortcut), which will place the shortcut on the desktop. The rest of the steps remain the same.