Function build_structure_tree_with_ui 

pub fn build_structure_tree_with_ui<F, U>(
    ui: &mut Ui,
    structures: &[(String, String, bool)],
    on_toggle: F,
    build_ui: U,
)
where
    F: FnMut(&str, &str, bool),
    U: FnMut(&mut Ui, &str, &str),

Builds the structure tree section with per-structure UI support.

When a structure is expanded, the build_ui callback is invoked to build the structure-specific UI (color picker, radius slider, etc.).