They will have similar cost,
in fact GidUtils::UpdateWindow CUSTOMLIB will call gid_groups_conds::actualize_conditions_window
I recommend you use GidUtils::UpdateWindow instead directly gid_groups_conds::actualize_conditions_window
because it use a common centralized syntax to update several windows (CUSTOMLIB, GROUPS, LAYER, …)
and the same for
GidUtils::OpenWindow, GidUtils::CloseWindow, GidUtils::ExistsWindow, GidUtils::ToggleWindow
(see comments on \scripts\dev_kit.tcl to know the names of windows for these hight level functions)
If you do several changes of the tree and do a final update the cost doesn’t matter, but don’t update it after each change, in this case must use some lower level function to not rebuild the whole tktreectrl widget)