If you wouldn't mind sharing, how do they let you customize it, and what do you enjoy about that?
The explanation for smoothing days is that it "[controls] how strongly each weight value affects the trend". It takes an positive integer value or 0. The recommended value is 7, but I ended up with 14. With higher values, both the forecast line and average line tend to be less dependent on recent weights and average out over a longer period.
The forecast days "[control] how many days to use for the forecast calculation. It doesn't specify what the acceptable range is, simply that the minimum value is 2 and the recommended value is 7. I ended up with a 14 here also. This value only impacts the forecast line, not the average line.
[1] On my phone, reached via Android's hamburger physical button. [2] Reached via a button that looks like the ai-settings icon from the http://www.androidicons.com/ set.
I do also have an advanced settings section for the forecast calculation, but it's good to know there's interest in controlling the MV factors too. Thanks for the feedback!