How to customize ckan header site navigation tabs

I would like to add extra header site navigation tabs to the default ones.

I have tried working with the solution given here but it is not working for me. I am getting Exception: menu itemapicannot be found error

This is my plugin.py code

import ckan.plugins as plugins
import ckan.plugins.toolkit as toolkit

class ApiPlugin(plugins.SingletonPlugin, toolkit.DefaultDatasetForm):
    plugins.implements(plugins.IRoutes, inherit=True)
    def before_map(self, m):
        m.connect('api', #name of path route
            '/api', #url to map path to
            controller='ckanext.kimetrica_theme.controller:ApiController', #controller
            action='api') #controller action (method)
        return m

This is my header.html code

{% ckan_extends %}

{% block header_site_navigation_tabs %}
  {{ h.build_nav_main(
    ('search', _('Datasets')),
    ('organizations_index', _('Organizations')),
    ('group_index', _('Groups')),
    ('about', _('About')),
    ('api', _('api'))
  ) }}
{% endblock %}

And this is my controller.py code

import ckan.plugins as p
from ckan.lib.base import BaseController

class ApiController(BaseController):
    def api(self):
        return p.toolkit.render('api.html')

I expect to have the api menu work like the rest of the menu do. I also have my template(api.html) in place

I solved this question by using ckanext-pages extension This extension allows you to add simple static pages and blogs and edit their contents.