In Odoo 14 Community Edition, you can indeed create server actions and contextual action buttons, even if you don’t have direct access to the server machine. Here’s a general approach to achieve this.
# Find the action from mrp.production

production_action = env['ir.actions.server'].search([('model_id.model', '=', 'mrp.production'), ('name', '=', 'Reserve')], limit=1)

# Check if action is found

if production_action:

    # Call the action

    production_action.with_context(active_ids=record.ids).run()

and Go to Settings > Technical > User Interface > Views.
you have to add button - button name="%(your_server_action_id)d" type="action" string="Reserve" class="btn-primary"/>