No slvs data when constraint is a contructor.

class_defines.py

@@ -2189,6 +2189,7 @@ def _name_setter(self, new_name):
     name: StringProperty(name="Name", get=_name_getter, set=_name_setter)
     failed: BoolProperty(name="Failed")
     visible: BoolProperty(name="Visible", default=True, update=functions.update_cb)
+    construction: BoolProperty(name="Construction")
     signature = ()
     props = ()
 
@@ -2314,6 +2315,7 @@ def draw_props(self, layout: UILayout):
         # General props
         layout.separator()
         layout.prop(self, "visible")
+        layout.prop(self, "construction")
 
         # Specific props
         layout.separator()
@@ -2339,6 +2341,12 @@ def placements(self):
         return []
 
 
+    def py_data(self, solvesys: Solver, **kwargs):
+        if self.construction:
+            return []
+        return self.create_slvs_data(solvesys, **kwargs)
+
+
 # NOTE: When tweaking, it's necessary to constrain a point that is only temporary available
 # and has no SlvsPoint representation
 def make_coincident(solvesys, point_handle, e2, wp, group, entity_type=None):

solver.py

@@ -121,10 +121,11 @@ def _get_msg_entities():
             # Store a index-constraint mapping
             from collections.abc import Iterable
 
-            indices = c.create_slvs_data(self.solvesys, group=group)
-            self._store_constraint_indices(
-                c, indices if isinstance(indices, Iterable) else (indices,)
-            )
+            indices = c.py_data(self.solvesys, group=group)
+            if indices:
+                self._store_constraint_indices(
+                    c, indices if isinstance(indices, Iterable) else (indices,)
+                )
 
         def _get_msg_constraints():
             msg = "Initialize constraints:"