I have to upload but I have to test it well before.
So, it is coming.
There are some adjustments in JDom and in the JS snipplet in your template.
The only thing is it will help you to skip the validation when you click to your custom task button.
To create a custom task :
example : item controller : 'produit'
task : 'run'
$task = 'product.run';
$icon = 'run';
$iconOver = 'run';
$alt = 'LANG_STRING_RUN';
$listSelect = false; //Check if an item is checked, when you are in a grid (collection)
JToolBarHelper::custom($task, $icon, $iconOver, $alt, $listSelect);
Add this code in the view file, next to the others tasks. displayXxxx() function.