I have found several posts that states that it's possible to modify the parameters of an action from a custom module the following way:

for the action open_create_project in the module project

<record id="open_create_project" model="ir.actions.act_window">

<field name="name">Create a Project</field>

<field name="res_model">project.project</field>

<field name="view_type">form</field>

<field name="view_mode">form</field>

<field name="view_id" ref="project_project_view_form_simplified"/>

<field name="target">new</field>

</record>

to modifiy it we create an action with an id such as original_module.id_of_the_action, so project.open_create_project in this case.

    <record id="project.open_create_project" model="ir.actions.act_window">
        <field name="name">New name for the action</field>
     </record>

And then we can add the fields that we want to change.

But I didn't found anything regarding this in the documentation of odoo. When I tried it it seems to work at first, but after another update of the custom module the change of the name seems to disappear sudently. So is this something that is supported or just a kind of hack that should be avoided?