This is not really a new feature. I made the first double-CCD firmware two years ago for a group of students in Germany. I forgot what they used it for, but they paid me in delicious german food.
I've since received a couple of requests for this feature from others, and rather than do a per-bratwurst-offering, I've decided to include it in the downloads-section at tcd1304.wordpress.com. There you'll also find a more in-depth walkthrough about considerations to make before changing the 4 or 5 lines of code required.
The long story short is that you can drive and read up to four CCDs with one STM32F401RE nucleo with an MCLK of 2,0 MHz. If you lower the CCD-clock, you can get away with up to eleven CCDs (my back-of-the-envelope calculations say). Of course you may run out of gpio's for ADC-input with that many CCDs, I haven't checked.
Anyway, here are some pictures.
One CCD is covered with M2-washers, the other with ball-point pen spring. Here's what's captured: