Xtykutl

I would like to 'transform' the action dropdown, that have the default delete option, in a single button, but keeping the rule of delete all the row that are checked.

You can achieve this by overriding the default action form as :

class CustomActionForm(forms.Form):

    action = forms.CharField(widget=forms.HiddenInput,

                             initial='delete_selected',

                             label='Delete Selected'

                             )

    select_across = forms.BooleanField(

                                       label='',

                                       required=False,

                                       initial=0,

                                       widget=forms.HiddenInput({'class': 'select-across'}),

                                       )

Then in your admin class define this as:

class YourAdminClass(admin.ModelAdmin):

     action_form = CustomActionForm

     ......

Now this custom action form will remove the action select dropdown and you would be able to use only delete_selected action.
It will look something like this:

If you want further customization in the template, you may consider overriding actions.html.

Hope this helps.