Specifies group index to filter text ranges (items).
property GroupIndex: integer;
GroupIndex is used to filter text ranges.
Text range Range will be added to the tree, if its rule (TTagBlockCondition) has DisplayInTree = True and:
(GroupIndex = 0) or ((Range.Rule.GroupIndex and GroupIndex) <> 0)
Using such filtering you may organize several different tree views for a single text.