Install this plugin to save time and complexity, you will not need to refactor your extra fields groups.
The plugin is integrated smoothly with K2 forms for categories and items, no need for extra forms or components.
Using this plugin, you can render mutliselect fields as checkboxes.
Its available also to order the select/multiseclt values alphabetically.
For whom using K2 for directory or lisiting purposes, you can use this plugin to show values of select/multiselect/radiobutton fields as images/icons, like in a resturant, club or hotel, you need to show features/facilities as icons.
Look at the demo to inspect all of these features...
First, edit the category to assign extra fields groups as required, you will select the main extra fields group as normal, then at the bottom of the category edit form, you can assign more extra fields groups.
Then, you will find all the extra fields, belongs to the assigned groups, in the extra fields tab of the item edit form.
And you will be able to display these extra fields in the front-end as normal.
This plugin is tested and working with Joomla 3 & Joomla 2.5 and K2 v2.6.x or later.
Recommended filter extension which is compatible and works with MEFG: Filter for K2 from Style Ware