I am reframing the question to be clarified.
I'm developing a theme and want to put an internal gallery. Do not want to use all photos uploaded to the media library. I want to create a field (checkbox) so you must select which of these photos should be in the gallery.
I'm using attachment_fields_to_edit attachment_fields_to_save and to add the checkbox, but to mark each picture you must click on "Show" and select the checkbox. I took a screenshot to show exactly where I want the checkbox to stay. http://imageshack.us/photo/my-images/146/checkboxwp.png/
Some time ago I saw a plugin that adds a checkbox next to the link "Show" to not having to open each one of the options and select the photos checkbox. I do not remember the name of the plugin, but it was what I wanted to do.
In other words, I add the checkbox next to the link "Show" for the user to click on this option and then click on "Save all changes"
Thanks and sorry if my explanation was not very clear.