I would like to change the protagonist's account balance depending on his income. Both are visible variables. Is it possible to say {account} = + {income} at the end of a chapter?
Depending on the specific situation, there might be workarounds. If you have only a few possible values for income, you could add one chapter option (link chapter) per income level and add the specific value there. The downside of that is that you can't really use those chapters for other decisions as you would need [number of income levels] x [number of other options] chapters. So it might be better to have a separate chapter for that calculation. It would also be possible to have one chapter for the payments with many different income levels as options. With a number to save the current position, you could allow the user to jump back to the current chapter. The disadvantage is that the reader would need to click 3 times to get the income. But the number of chapters would be limited to 2 + [number of income levels] + [number of saved destinations]