Add documentation for addColumns in host/service list views

fixes #2579

modules/monitoring/doc/01-About.md

@@ -7,3 +7,4 @@ Please read the following chapters for more insights on this module:
 * [Security](06-Security.md#monitoring-module-security)
 * [Restrict Custom Variables](10-Restrict-Custom-Variables.md#monitoring-module-restrict-access-custom-variables)
 * [Hooks](20-Hooks.md#monitoring-module-hooks)
+* [Add Columns to List Views](11-Add-Columns-List-Views.md#monitoring-module-add-columns-list-views)

modules/monitoring/doc/11-Add-Columns-List-Views.md

@@ -0,0 +1,32 @@
+# Add Columns to List Views <a id="monitoring-module-add-columns-list-views"></a>
+
+The monitoring module provides list views for hosts and services.
+These lists only provide the most common columns to reduce the backend
+query load.
+
+If you want to add more columns to the list view e.g. in order to use the URL in
+your dashboards or as external iframe integration, you need the `addColumns` URL
+parameter.
+
+
+
+Example for adding the host `address` attribute in a host list:
+
+```
+http://localhost/icingaweb2/monitoring/list/hosts?addColumns=host_address
+```
+
+![Screenshot](img/list_hosts_add_columns.png)
+
+
+
+
+Example for multiple columns as comma separated parameter string. This
+includes a reference to the Icinga 2 host object custom attribute `os` using
+`_host_` as custom variable identifier.
+
+```
+http://localhost/icingaweb2/monitoring/list/services?addColumns=host_address,_host_os
+```
+
+![Screenshot](img/list_services_add_columns.png)