Addendum: During the second stage "Contraction", here is another step to add:
6) Sensitivity test and optimization: feel free to tweak the indicators' parameters, not only to try to find parameters that better fit your strategy, but also to see how the parameters change the indicator's result. This is a common practice in machine learning and statistics to evaluate how much a model is sensitive to parameters and noise, with models that vary less in their results despite parameters change being considered more robust. Also, different set of parameters can make the same indicator detect different kind of signals, eg, a trend indicator can sometimes be converted into a market cycle indicator by increasing the lookback period and other paramaters.
Addendum about the neural expansion and contraction processes, as I realize I didn't explain enough what their purposes are:
* neural expansion create all kinds of neurons and synaptic connections to try to find ways to complete the task we are trying to learn, essentially, it's a "throw anything at the wall and see what sticks" approach.
* Neural contraction is the complementary next step: once our brain found something that works, it will try to optimize it, to make it more efficient, by removing the fluff out of the necessary, in practice by removing synaptic connections that are redundant or even worsening results. It's the same as the difference between someone learning a thousand different kinds of punches, and one who spend years mastering a few ones, the one who mastered a few ones will likely be much more powerful and efficient despite having a less diverse palette.
Of course, there is a trade-off: you don't want to be too restricted, too narrow, but at the same time you want to stick to the minimum to avoid the fluff that can confuse your decision taking process. In computer science, this is called the "exploration-exploitation trade-off", and is usually solved by 1) using an iterative process, 2) leaving some room for new approaches to be tested. Both of these steps are implemented in the process I presented above.