Preserve authored projection content and contextual canvas selection

docs/api.rst

@@ -570,8 +570,15 @@ retain their identities and contracts; migration does not silently replace them.
 ``coverage`` and ``work_contexts``, and ``Name`` for ``exchange_labels``.
 ``{"Only":[]}`` hides all relation and trace lines; ``{"Any":[]}`` preserves
 an explicit empty category/context selection. Category members union within
-each family, and independent filters intersect. ``Traceability`` permits
-references from both layers; ordinary projections require the diagram's layer.
+each family, and independent filters intersect. String projections permit saved
+references and placements from both layers. Only ``Traceability`` renders both;
+other string projections filter to the diagram's declared layer. ``EditDiagram``
+may change between these projections without deleting latent placements, routes
+or visibility choices. Returning to Traceability restores their applicability.
+Typed StateMachine/Scenario views retain their strict membership and layer checks.
+Missing objects, wrong reference kinds/families and duplicate selections remain
+invalid. Frozen versions 1–6 keep their prior layer admission before migration;
+older version-7 implementations may reject these newly accepted ordinary views.
 These presentation choices preserve semantic records, routes, placements and
 the automatic port positions derived from unfiltered eligible exchanges.