I’m not going to add a form-tag for a hidden field to the plugin, but it would help other users if you publish your code somewhere.
I used to have my own shortcode for CF7. But when a major update would come my little addition would vanish and I had to reinsert again.
I even tried to insert my own shortcode within my function file but I thought I was making too much of something little.
So, since I do not need to use hidden fields in all of my contact forms I insert the following code only when I need it (for the simple stuff) at the very beginning of the form (or at the bottom before the submit button, wherever appropriate)
<script>
var thisYr = 2016;
var nextYr = thisYr + 1;
document.write('<input type="hidden" name="year" value="' + nextYr + '" />');
</script>
and I just call this hidden field at my email form as [year]
I am using javascript because I am calculating few numbers that I needed. I suppose just entering HTML code will do just fine if you do not need to calculate.
