In SharePoint 2013. My workflow requires that the user edit a task, fill in a field, and click a "Completed" button which then changes a "Task Status" dropdown to "Completed". Once the dropdown changes to completed it kicks off the rest of the workflow. I would like to hide this dropdown from the user to avoid confusion but still have it functional. Is this possible? Also, if it's possible it would be nice to hide the "Save" button as well.
Small bit of jquery should do the trick for you here.
Just put this in a content editor web part on your edit form. Just be sure and change the link source of jQuery to the location on your site.