Can't set 'colorbar' parameters in layout.template.data.{trace}[i].{line|marker} #4467

Setting colorbar parameters doesn't appear to work in layout.template.data.{trace_type}[i].{line|marker}.

Related: #3100 (comment), to quote @etpinard:

As for the colorbar part, the problem comes from the colorbar defaults call:

plotly.js/src/components/colorscale/defaults.js

Line 62 in d340150

if(showScale) colorbarDefaults(containerIn, containerOut, layout);

where containerOut is fullData[i] for heatmap, but is fullData[i].marker for scatter and other marker colorscales. Colorbar templates propagate correctly (using Template.newContainer) from fullData[i], but not from marker containers. Adding

should be enough to fix this, but we should look for other situations where supply-defaults subroutines are called with trace sub-containers.

I'm not sure the above suggested fix was ever implemented.

This codepen demonstrates the issue with ypad:
https://codepen.io/wbrgss/pen/NWPXEPG

I logged a separate issue related to #3100 in #4466