From whatever I have experienced, there are two kind of mental models provided by programming tools, simple (e.g. dplyr) and complex (e.g. pandas). If used sparingly, most complex tools are really annoying unless, of course, you clearly understand the idea behind the models they expose. Here are some tools in that category which I would like to study very thoroughly sometime:

• ☐ Matplotlib. Maybe the recent updates made the API cleaner. A good resource to start might be this.
• ☐ $$\LaTeX$$ is irritating and is almost everywhere. Going through the recommended wikibook might help. Also LaTeX and Friends has good coverage of TikZ too.
• TikZ. Inkscape has pretty weak scripting capabilities.
• Regex. I specifically need to understand how it works to really appreciate it.