Hello,
Apologies for late reply, I’ve been in the middle of a busy period ( moving out to a new house ) so free support has been left behind for a bit.
Regarding your question, i’m afraid this isn’t possible right now. The pro version doesn’t include this feature either.
If you have some coding knowledge you can easily extend the plugin and integrate the feature yourself or hire someone who can do it for you.
What I’d suggest you to do in your case is to first create a secondary price field for your menu items, and then customize the templates of the plugin to display your different pricing situation.
In order to add new fields to the menu items backend, you need to use the following wp filter wprm_menu_item_details_metaboxes_fields
see here for usage and parameters https://github.com/alessandrotesoro/wp-restaurant-manager-lite/blob/master/includes/metaboxes.php#L37
Once you’ve added your custom field you can customize the templates to display your new pricing – read here on how to customize the templates https://support.themesdepot.org/hc/en-us/articles/201730421-Customizing-WPRM-
Hope this helps,
Regards.