Hot answers tagged layers
You will need to use ArcObjects. You are looking for the IDisplayExpressionProperties interface. It is obtained from IDisplayString, which in turn is obtained from IFeatureLayer. Here you will find a fantastic little snippet of code provided by patrick that does the trick: public void annotateLayer(ILayer thisLayer, String geocode, double minScale, double ...
If you're writing a geoprocessing script, I'd recommend authoring a .lyr file you bundle with your toolbox and set the symbology in the script tool parameters to point to the .lyr file (see the "Symbology" part of the dialog).
You can show as many categories as you want in one layer, but you'll have to do some custom coding. My approach would be: Start with as many categories as you can using the Category Visualization Wizard (which I assume you're already doing). Click the CSS icon on the sidebar. This takes you to the CartoCSS editor. Here you can copy and modify the style ...
The QGIS project file can be edited with any text editor. So you can look into it, and remove the layer entry that does not show up in the table of content. The file has a XML structure, so be sure to catch the closing tag as well. To be safe, make a copy of the project file before editing.
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