There's a UISystem now for to compliment the entities and components in GUECS. I now use that to do the drag/drop transfers instead of raw code right in the FSM.

gui/uisystems.hpp

@@ -0,0 +1,10 @@
+#pragma once
+#include <guecs/ui.hpp>
+#include <optional>
+
+namespace UISystem {
+  std::optional<guecs::Entity> loot_grab(guecs::UI& gui, guecs::Entity gui_id);
+
+
+  bool loot_drop(guecs::UI& source, guecs::UI& target, guecs::Entity grab_source, guecs::Entity target_id);
+}