Yet another way to extend html?

[Ivan Z.]

Hi, all!

There is a restriction here:

With Jinja2, the content is produced in one step, with no possibility of post-processing. The only way left to alter the generated content is to perform these modifications dynamically on client-side using JavaScript.

-- https://trac.edgewall.org/wiki/TracDev/PortingFromGenshiToJinja

Have you considered the option of inheriting a template with the same name?

Here is an implementation based on Jinja for Sphinx-doc:

Templates with the same name in the templates_path override templates supplied by the selected theme.

-- https://www.sphinx-doc.org/en/master/development/templating.html 

Another example is based on Django templates:

A Django reusable app providing the overextends template tag, a drop-in replacement for Django's extends tag, which allows you to use circular template inheritance.

-- https://github.com/stephenmcd/django-overextends

It seems like it is possible to extend/replace any block of any jinja-based template with the same name by any trac-extension without client-side rendering.