Hi Isomorphic,

please see this online sample (SNAPSHOT_v12.0d_2017-08-13) with textMatchStyle: "substring" added:
Code:
isc.DynamicForm.create({
    width: 500,
    numCols: 4,
    isGroup: true,
    groupTitle: "List - ComboBox",
    wrapItemTitles: false,
    fields : [{
        name: "bugStatus", title: "Bug Status", 
        editorType: "ComboBoxItem",
        valueMap : {
            "new" : "New",
            "active" : "Active",
            "revisit" : "Revisit",
            "fixed" : "Fixed",
            "delivered" : "Delivered",
            "resolved" : "Resolved",
            "reopened" : "Reopened"
        }
    },{
        name: "itemName", title: "Item Name", editorType: "ComboBoxItem", 
        optionDataSource: "supplyItem", pickListWidth: 250, operator: "iContains", textMatchStyle: "substring"
    }]
});
Now if you search for "roll":
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Name:	ComboBoxItemSearch.PNG
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Size:	6.9 KB
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It would be great that if you enter "roll", all the "roll"-substrings from the results would be highlighted, like it happens e.g. here in google Analytics:
Click image for larger version

Name:	googleAnalyticsHighlight.PNG
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Size:	9.1 KB
ID:	248390

This is of course minor and might be tough with ComboBoxItems with more complicated criteria, but is a nice GUI feature nevertheless.
Perhaps internally, ListGridField will get a new API "setTextToHighlight(String text)" that will get applied to the DropDown ListGrid?
That way, also ListGridFields in normal ListGrids displaying a filterRow could benefit from it.

Best regards
Blama