There’s likely a better way, but I was able to do this by using jQuery to target the button which normally triggers the desired mass action and then forcing a click on it. Here’s my code:

var $ = skuid.$,

    action = argumentse0].action,

    list = argumentse0].list,

    model = argumentse0].model; // Force all checkboxes (for each table row) into checked state

$('#sk-3GF2wd-4635 inputntype=checkbox]').prop("checked",true); // Trigger a click on the button which triggers the mass action

$("#followupTable div.nx-massactions div:eq(0)").click(); 

I found the selector for the checkboxes and the mass action using Chrome’s devtools. There are a lot of guides around if you’re unsure of how to do this yourself. Here’s a decent one.

Here’s how I attached the snippet to a save button on my layout:

Hope this helps and I’m happy to help clarify if needed. Also curious if anyone found a “nicer” way of doing this.

Kathryn,
Thanks for posting this! You might find this method a little “nicer”, as it doesn’t require manually picking out DOM elements:

var $ = skuid.$, list = argumentsu0].list, selectedItems = list.getSelectedItems();

selectedItems should return information about the associated element, row, etc.
Hope this helps!
Emily