Add it to the end of the target in the shortcut or you can do it from the command prompt. Put a space between "exe" and "-dx11" or Windows is going to tell you the filename is wrong.

On top of what DoomSooth said, keep in mind that if there's a space in the path it'll be between quotes, in which case the arguments must be outside of it.
ex (assuming it's Thymesia.exe):
D:\Games\Thymesia\Thymesia.exe -DX11
but
"D:\My Games\Thymesia\Thymesia.exe" -DX11

Hmmm... No quotes in mine. Must be a Windows 10 or 11 thing.

Can you elaborate on that? ;)

Bots are not the elaborating type... ;)

Yeah, I know, but lately I accused two users of being bots, and then it turned out that they weren't native speakers and just phrased their posts unusually.
Now I reassure that they are actually bots. Just hadn't the time for a full Voight-Kampff- test this time.

Mafia Definitive Edition works fine (so far) with the latest dxvk release.

I was only able to find the Linux version of dxvk. Is there a special version for Win 7 or is there only one version for both OS?

Yes, officially only Linux is supported by the devs, but since they distribute compiled dlls for usage with WINE, it works on Windows too.

Is there a manual how to install and configure it on a Win 7 machine? I'd like to link it here for the people who are clueless like me :)

Don't know. But it's relatively simple:
-download the latest release
-Mafia DE uses 64bit dx11, so you have to extract dxgi.dll and d3d11.dll from x64 into the game folder where the game exe resides
-optionally you can configure dxvk via a dxvk.conf, which is placed beside the dlls.

Thanks, I´ll link your post.

'In sound mind' works on Windows 7.

2077 still runs in Windows 7, after updating to 1.6.