Fix indentation of leaf items in hierarchical lists

[abey79]

What

• Fixes Fix indentation of leaf ListItem #5457 (introduced in Fix ListItem indentation so icons are properly aligned #5340)

Also sneaks a minor UI tweak in the plot marker selection list.

Before/after:

cc @martenbjork

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
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