Just having a go at this myself my reading up on the code ( I am no coder)
So far not looking at how pretty it looks atm I just want to get the collapse working.
This is what I have done so far.
On line 15/16 I have added the below code (in file main/views/themes/tastyigniter-orange/partials/menu_list.php)
<button type="button" class="btn btn-info" data-toggle="collapse" data-target="#demo">Simple collapsible</button>
<div id="demo" class="collapse">
This kinda works, it puts a button next to menu items however when you press the button it just collapse the first category
Im going to keep plugging away because I desperately want this feature asap haha!