gui.dragElement

Drag from one UI element to another by their elementTree ids - press at the centre of the part of the first one the last frame drew, move to the second, release. For sliders, reorderable lists, and drag-and-drop.

Both ends are resolved before anything moves, and the drag is sent only while ui.diagnose reports painted for each of them. An end the frame left undrawn comes back as { ok = false, from, to, reason, detail, error } carrying that end's verdict.