elgg_extend_view('page/elements/sidebar','members/sidebar');

where members/sidebar is a file with your own code located in:

mod/your_plugin/view/default/members/sidebar.php

Thanks RvR,

is it NOT possible to put other plugin views, in this case the member plugin, vissible in the aside?

You can extend a view with a view provided by another plugin, e.g.

elgg_extend_view('page/elements/sidebar','members/sidebar');

Maybe that's the view you meant? But this view would only add a search box for members to the sidebar (and with only the above code without checking the context this box would appear twice on the members page).

The view you want to use, must contain the code for the functionality you have in mind. And the members plugin offers no view that suits (the resource view in the plugin would add the whole members page to the sidebar).

The easiest thing would be to add your own view in your plugin for getting exactly the content you want to be added. Two examples you might want to study:

• my Users Online plugin has an option to list the users currently online in the sidebar (also by extending the 'page/elements/sidebar' view). It lists only users active within the last 5 minutes and shows only their avatars to keep the space needed small. But it wouldn't be difficult to change the code to show for example the most recent new users instead.
• within the Widget Manager plugin there's a widget for the index page included that list most recent users (code in the file widget_manager/views/default/widgets/index_members/content.php). You can take this code as basis for your own view if you want the users listed in this way.

If you code has no effect it might be because you have the caching mechanisms of Elgg enabled. You would either need to flush the cache or to disable the caching during development to see the results of your changes.