Drop object on the plate (#6166)

Co-authored-by: SoftFever <softfeverever@gmail.com>

src/slic3r/GUI/Plater.hpp

@@ -529,6 +529,7 @@ public:
     //BBS: add clone logic
     void clone_selection();
     void center_selection();
+    void drop_selection();
     void search(bool plater_is_active, Preset::Type  type, wxWindow *tag, TextInput *etag, wxWindow *stag);
     void mirror(Axis axis);
     void split_object();