does not seem supported, but you can have multiple config files if that helps:
$ dosbox --help
Usage: dosbox [OPTION]... [FILE]
These are common options:
-h, --help Displays this message.
--printconf Prints the location of the default configuration file.
--editconf Open the default configuration file in a text editor.
-c <command> Runs the specified DOS command before running FILE.
Multiple commands can be specified.
-conf <configfile> Start dosbox with the options specified in <configfile>.
Multiple configfiles can be present at the commandline.
-userconf Load the configuration file located in
~/.config/dosbox. Can be combined with the -conf
option.
-fullscreen Start dosbox in fullscreen mode.
-lang <langfile> Start dosbox with the language specified in
<langfile>.
-machine <type> Setup dosbox to emulate a specific type of machine.
The machine type has influence on both the videocard
and the emulated soundcards. Valid choices are:
hercules, cga, cga_mono, tandy, pcjr, ega, vgaonly,
svga_s3 (default), svga_et3000, svga_et4000,
svga_paradise, vesa_nolfb, vesa_oldvbe.
-exit Dosbox will close itself when the DOS program
specified by FILE ends.
-v, --version Output version information and exit.
You can find full list of options in the man page: dosbox(1)
And in file: /usr/share/doc/dosbox-staging/README