Solved the server action issue!

The problem is how do you create a server action: if you create it by GUI then you don't have an external ID but just an ID number, while if you create via XML you can use the ID name as a button name and Odoo will assign automatically an ID number.

I have a server action called rest_checkout_send, then on button name I wrote

<button name="%(rest_checkout_send)d" string="Enviar" type="action" attrs="{'invisible':[('status','=','1')]}"/> 

and it was automatically update in

<button name="723" string="Enviar" type="action" attrs="{'invisible':[('status','=','1')]}"/>           	   

 That's simply perfect!