You should be able to load a form in a lightbox, yes. Try using a link of this format:
Code:
return '<a href="http://yourdomain.com/index.php?option=com_fabrik&view=details&formid=1&rowid={participants___id}&iframe=1&tmpl=component" rel="lightbox[participants]">{yourlist_establishmentname}</a>';
Replace the placeholders and formid as per your previous link.
NOTE - if you don't have any image or upload elements on your list, you'll need to update form github, as I've added a new choice to the "Include lightbox js" global option (parameters button, top right of Lists tab on backend). Previously, even if you have "Yes" selected for that, we would only include the lightbox JS if there was an element on the page which needed it. I've modified that so the choice is now No / Auto / Yes, where Yes now always loads, regardless of elements being used.
I also strongly suggest using Mediabox instead of Slimbox, see the option immediately above the one I just described in the params.
Note that you should also automagically get a Next / Prev button on the Mediabox popup, which happens by putting a group name in the rel='lightbox[something]'. The 'something' can be any word, it just tells Mediabox "treat any links which use this group label as being grouped with Next/Prev buttons".
I can't guarantee you won't have issues displaying certain element types in Mediabox, like I haven't tried it with Google maps.
Also, if you then ask "how do I make the lightbox close automatically after I submit a form", the answer is "I don't know". But if you just use this for details view, that won't be an issue.
If this works, you can remove the init code for the Fabrik window code you added earlier in this thread.
-- hugh