create a bat file that runs dosbox with the options you want.
Think this is what IDSoftware as well

Ok, I just quickly tried that out, turns out that Steam only looks at executables (*.exe) or shortcuts to executables only 🙁

Would've been great if there was a "All Files" option in the open window, but it's just *.exe only.

EDIT: Thinking about it, can you treat a batch file as an executable? as in turning .BAT into .EXE? I'll try it out, but I doubt it...

EDIT2: And no... Windows didn't like that, 🤣. Still if it did work it would be a clever way to trick Steam into running a batch file rather than an executable.

I don't have it handy at the moment, but offhand, isn't there a field where you can enter "-conf themeP.conf " as a parameter ? (That's the way it works for Source engine games.)

Otherwise, it is a fairly trivial matter to write a Python script that will launch things appropriately, and to compile the script into an EXE. It's not even remotely elegant, but it is fairly trivial.

Yes, but only in Steam games...

SepticLemon wrote:

The ironic thing is, Steam games you buy give you and option to add a command though the "Launch options" setting in the properties, but you can't do this for Non-steam games. Now, what I can see is a "Target" and a "Start in" in the properties for Non Steam games, and yes I tried to do "C:\Games\DOSBox-0.74\DOSBox.exe -conf themeP.conf" in the Target, but I end up with an error assuming that Steam believes that "-conf themeP.conf" is a part of program name rather than a command.

Which is dumb indeed, especially if you have non-steam games that might need parameters like the ABA games.

You could try tricking STEAM by playing around with quotes, like for example:
"C:\Games\DOSBox-0.74\DOSBox.exe -conf themeP.conf"
""C:\Games\DOSBox-0.74\DOSBox.exe -conf themeP.conf""
'C:\Games\DOSBox-0.74\DOSBox.exe -conf themeP.conf'
etc.

If STEAM insists on an exe you could use a scripting language with a "compiler", as Jorpho suggested. I would use AutoIT, as I'm already quite familiar with the language. The problem with this approach is that you'd need one script/exe for each game. An "all in one" script would probably be much easier to use (and maintain). With some nifty programming, like for example by querying the current directory (which can be set via the STEAM shortcut, as you say), implementing an "all in one" script could be possible.

Another solution would be to create separate DOSBox directories for each game, and put the respective conf in each dir with a filename of "dosbox.conf". AFAIK, if DOSBox can't find a "dosbox.conf" in the current user's profile dir, it will use the one in the current directory.

Ah ha! Got it!

Ok, I really do appreciate you guys helping me out! ADDiCT had a solution, even though it wasn't 100% right.

This is how it works...

Target: "C:\Games\DOSBox-0.74\DOSBox.exe" -conf themeP.conf

The Parameters go OUTSIDE AND AFTER the quotations!

Even if you guys didn't give me the exact solution, at least you put me the right direction! Thanks guys!

EDIT: With this I can use parameters in other games such as ABA's Torus Trooper, without the parameters, all you get is fullscreen in 800*600, ick, but now I can use -res 1280 1024 after the quotations, it now makes Steam much more flexible!