selectableBranches property
Whether a node that has children may itself be chosen.
Off by default, which is the shape most of these trees have: the branches are the taxonomy and the leaves are the answers, and a "Europe" held alongside "France" is usually a data model nobody meant. A node's own PlTreeSelectNode.selectable overrides it either way, and a branch that cannot be chosen still opens and closes — pressing it is how you get at what is under it.
Implementation
final bool selectableBranches;