Render custom template

In C# web forms, there is something like a master-page within which you can embed your individual aspx pages. I want to display a custom text message along with a link. So i’ve created an html template inside the plugins template directory and renderin it using the reder_plugin_template method. But it only displays plain vanilla text. How do I display it inside the indico web page (menu bar side bar design elements etc.) . I’m new to jinja templates. Thanks.

You would need to give more details where exactly you want your output to appear.

There are template-hooks available for some parts (run git grep template_hook | grep html on the source code to see what is available.
Other places are harder to override (possibly providing override templates etc.), you can take a look at the indico and indico cern plugins for inspiration.

Thanks, for example, I could use the standard template that is currently being used to display HTTP error response notifications like “Not Found” and instead display my custom text there. (attached image) How do I go about this?

There you need template customization, check Settings — Indico 3.2.7 documentation for a start…