Thank you, @Daniel_Stieber! I would love to hear more comments once you are able to take a deeper dive.
As for the feature/bug question, I think there are two competing features that make it looks like there’s a bug. First, the recalculation on the fly, as the slider is slid, is actually a very cool feature. It actually recalcs pretty fast, and it allows you to instantly see the effect of a change on the bottom line numbers. Second, the bar chart animates the bars growing out of the base whenever the chart is changed. The problem is that the animation takes a second to complete, so as you slide a slider, the animation keeps restarting but does not fully finish until you stop moving the slider. The result is a herky-jerky action on the chart that looks like a bug. IMHO, it would be better if Coda nixed the animation on the chart so that as the slider is moved, the bars on the chart would instantly move to their new positions in response to moving the slider, creating a kind of animation effect that the user is controlling with the slider.
I have added a suggestion to Coda about this situation.