Bug report #19097
Data defined size legend symbols do not show if you use a field or an expression to scale the symboŀ, and not the DD assistant
|Affected QGIS version:||3.1(master)||Regression?:||No|
|Operating System:||Easy fix?:||No|
|Pull Request or Patch supplied:||No||Resolution:|
|Crashes QGIS or corrupts data:||No||Copied to github as #:||26927|
If you scale a point symbol size with the data-defined override feature, and you'd later want to display the scales in the legend or layer tree, you'll be able to get a sized symbol legend only if you used the data-defined assistant. Using an existing field or an expression (even when you copy the one returned by the assistant dialog) does nothing: the legend ignores the scaling and seems to be triggered by only the assistant dialog.
This makes the feature less interesting and a bit shaky.