Just know that there are two versions of the UI in memory, one in the form that it was loaded from disk, and one which is the collection of all windows loaded into the active UI (i.e. on which a /show_window was done either manually or automatically). All your active windows reside in the same subtree (root._HUD), even if on disk they are in separate subtrees/modules (e.g. root.MainHUD and root.Custom).
You can manipulate both of them, but for it to affect currently active windows you need to manipulate those in the _HUD tree. For changes to persist across characters during the session they need to be (also) made to the other non-active trees.
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