Hi xan@jmp,
I was recently searching this topic because I found an example of a "broken-axis" graph and wanted to recreate it without using Microsoft Office products. The paper located at the following link contains a graphical abstract showing IR spectra for modeled and experimental vibration energy for essential oils found in nutmeg (e.g. eugenol). In this case, the authors were attempting to point out different areas of the IR spectrum where certain important peaks were located. These data are usually recorded from 4000 - 20 cm-1 and are plotted with either % transmittance or absorbance on the y-axis. Here, I suppose two graphs would work, but it creates a sense of discontinuity in a continuous spectrum. Generally people use a broken x-axis graph that essentially skips areas of the full IR spectrum where there is no significant absorbance or change in %T. I think this is a similar example to what you've found in your blog post. Thought you'd be interested.
I have been using a combination of Excel and Powerpoint to create my custom graphs. Usually works well, but is time consuming.
Here is the link http://pubs.acs.org/doi/10.1021/acs.jpca.5b07607
~m