Sorry that I have to come back to TWebTreeView. It's working for a great deal, but..
node := WebTreeView.Selections[400]; // doesn't compile ; property not shown in VSC
WebTreeView.FullExpand; // doesn't compile ; property not shown in VSC
WebTreeView.FullCollapse; // doesn't compile ; property not shown in VSC
n := WebTreeView.Items.Count; // result is 3 where it should be 1854 in my case
node := WebTreeView.Items[400]; // result is null
WebTreeView.Selected := node; // doesn't open the tree and show the selected node, check https://www.synbiosys.alterra.nl/testtree