One trick I like to use is to add another combination, set it to markers and the colors to transparent
I have two data items in that combination, min and max, set to -0.5 and 1.5 respectively. And unchecking "Include Zero" in the axis range. By doing so I get a little bit of finer control over exactly how the axis appears. It's not perfect because the graph automatically tries to "pretty fit" the axis. I set the chart node member to Text and " " so it doesn't affect the legend. The cool thing with this is you can add a prompt that let's the user select whether to make the chart 0 based or not (which 99% of the time it should absolutely be).
Something like:
#let zerobased = prompt('make0Based','token','Yes');
case zerobased
when 'Yes' then '0'
else '[% of plan] * 0.9'
end#
This trick also works if the data is all 0s:
