I couldn't find anywhere that this or something equal was implemented, so I went about adding it for my app.
In dataface/Dataface/SearchForm.php around line 131 -
if ( $this->_table->isPassword($name) ) continue;
//kk Add visibility:find attribute (to hide field)
if ( $field['visibility']['find'] == 'hidden' ) continue;
// add the field to the form
Apologies if this is already in there and I missed it.