I already answered your support ticket on the subject. For your convenience I will paste my answer here as well:
1. You can achieve this functionality by simply removing the following line of code from the CustomFilterDescriptor class:
This will disable the filtering logic, however, the highlighting part will work.
2. The filtering functionality will not work in the same way as in RadGridView, so I am afraid that you can not achieve it using our RadTreeListView.
this.compositeFilterDesriptor = new CompositeFilterDescriptor();
this.compositeFilterDesriptor.LogicalOperator = FilterCompositionLogicalOperator.Or;
foreach (GridViewDataColumn column in columns)
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