Hi,
I understand you issue. Probably it is not working, else you will not ask here:) I can look at this in one of next updated. I understand that you have already created configs, but maybe will be faster use Magic Dosbox gui for mounting images. Then you can scroll to “Software section” and export autoexec to clipboard (if you really want use expert settings). Paste then clipboard in expert settings and modify.
Best regards,
Tony