Google Sheets – Add Generated QR Code to Avery Mail Merge Template in Google Docs

At this time it's not possible to change the default row height. One workaround is to use Google Apps Script to change the row height. You could use on change installable trigger to call the script every time a new sheet or row is added.

Note:
If the cell includes breaklines, or it's wrapping setting is set to wrap it's not possible to adjust the row height to a height less than the required to by its content. See https://issuetracker.google.com/issues/36765452

Stepped area chart does not support variable width of steps. But you can use the ordinary area chart like this:

The data provided to this chart was as follows. The first column was marked for "use as labels" when inserting the chart.

0.00    0
1.00    0
1.00    1
1.41    1
1.41    2
1.73    2
1.73    3
2.00    3
2.00    4
2.24    4
2.24    5
2.45    5
2.45    6
2.65    6
2.65    7
2.83    7

The idea is that each x value is repeated twice, and each y value is repeated twice, but they are half-step out of sync with each other. So every time we move down the rows, exactly one of two coordinates changes: x (horizontal segment) or y (vertical segment).

For the record, the formulas were =sqrt(floor(row()/2)) and =floor((row()-1)/2) and the chart options were