diff --git a/src/gui/interact/ui-coord.hpp b/src/gui/interact/ui-coord.hpp
index 8a6dd575c..dc8e9972e 100644
--- a/src/gui/interact/ui-coord.hpp
+++ b/src/gui/interact/ui-coord.hpp
@@ -249,7 +249,8 @@ namespace interact {
       void
       setComponent (UIPathElm idx, Literal newContent)
         {
-          UNIMPLEMENTED ("forcibly change data, maybe extend storage");
+          Literal* storage = maybeExpandTo (idx);
+          setContent (storage, newContent);
         }
       
       
@@ -295,7 +296,7 @@ namespace interact {
       
       /* == Builder functions == */
       
-      Builder&&
+      Builder
       window (Literal windowID)
         {
           uic_.setComponent (UIC_WINDOW, windowID);
@@ -303,15 +304,15 @@ namespace interact {
         }
       
       /** augment UI coordinates to mandate a specific perspective to be active within the window */
-      Builder&&
+      Builder
       persp (Literal perspectiveID)
         {
-          uic_.setComponent (UIC_PART, perspectiveID);
+          uic_.setComponent (UIC_PERSP, perspectiveID);
           return std::move (*this);
         }
       
       /** augment UI coordinates to indicate a specific view to be used */
-      Builder&&
+      Builder
       view (Literal viewID)
         {
           uic_.setComponent (UIC_VIEW, viewID);
@@ -319,7 +320,7 @@ namespace interact {
         }
       
       /** augment UI coordinates to indicate a specific tab within the view" */
-      Builder&&
+      Builder
       tab (Literal tabID)
         {
           uic_.setComponent (UIC_TAB, tabID);
@@ -327,7 +328,7 @@ namespace interact {
         }
       
       /** augment UI coordinates to indicate a tab specified by index number */
-      Builder&&
+      Builder
       tab (uint tabIdx)
         {
           uic_.setComponent (UIC_TAB, Symbol{"#"+util::toString (tabIdx)});
@@ -336,21 +337,21 @@ namespace interact {
       
       
       /** augment UI coordinates to define a complete local path */
-      Builder&&
+      Builder
       path (string pathDefinition)
         {
           UNIMPLEMENTED ("set path");
         }
       
       /** augment UI coordinates by appending a further component at the end */
-      Builder&&
+      Builder
       append (Literal elmID)
         {
           UNIMPLEMENTED ("mutate: append");
         }
       
       /** augment partially defined UI coordinates by extending them towards the root */
-      Builder&&
+      Builder
       prepend (Literal elmID)
         {
           UNIMPLEMENTED ("mutate: preprend");
diff --git a/src/lib/path-array.hpp b/src/lib/path-array.hpp
index 2e2d3ecb5..8a0071fa7 100644
--- a/src/lib/path-array.hpp
+++ b/src/lib/path-array.hpp
@@ -101,7 +101,7 @@ namespace lib {
         PStorage
         newCopy()  const
           {
-            size_t siz = size (unConst(this)->storage_);
+            size_t siz = 1 + size (unConst(this)->storage_);
             const char** alloc = new const char*[siz];
             std::copy (storage_, storage_+siz, alloc);
             return reinterpret_cast<PStorage> (alloc);
@@ -198,9 +198,20 @@ namespace lib {
           }
         
         void
-        trimTo (size_t cnt)
+        resizeTo (size_t cnt)
           {
-            REQUIRE (cnt <= size());
+            if (cnt > size())
+              { // copy to expanded storage
+                auto target = new const char* [cnt+1];
+                auto pos = std::copy (storage_, storage_+1+size(), target);
+                for ( ; pos < target+1+cnt; ++pos)
+                  *pos = nullptr;
+                if (storage_)
+                  delete[] storage_;
+                storage_ = reinterpret_cast<PStorage> (target);
+                size (storage_) = cnt;
+                return;
+              }
             if (not storage_) return;
             if (cnt == 0)
               {
@@ -437,6 +448,22 @@ namespace lib {
           return const_cast<Literal*> (elm);
         }
       
+      /**
+       * @internal ensure storage for the indicated position exists
+       * @return pointer to the storage, either existing or reallocated
+       */
+      Literal*
+      maybeExpandTo (size_t idx)
+        {
+          if (chunk_size <= idx and size() <= idx)
+            tail_.resizeTo(idx+1 - chunk_size);
+          if (idx < chunk_size)
+            return elms_.begin() + idx;
+          
+          ENSURE (idx-chunk_size < tail_.size());
+          return const_cast<Literal*> (&tail_[idx-chunk_size]);
+        }
+      
       /** @internal force new content into the given entry */
       void
       setContent (Literal* pos, const char* val)
@@ -487,9 +514,9 @@ namespace lib {
             setContent (getPosition(idx), nullptr);
           
           if (idx >= chunk_size-1)
-            tail_.trimTo (idx+1 - chunk_size);
+            tail_.resizeTo (idx+1 - chunk_size);
           else
-            tail_.trimTo (0);
+            tail_.resizeTo (0);
         }
     };
   
diff --git a/tests/gui/interact/ui-coord-test.cpp b/tests/gui/interact/ui-coord-test.cpp
index ae73197a0..0ebebb4ed 100644
--- a/tests/gui/interact/ui-coord-test.cpp
+++ b/tests/gui/interact/ui-coord-test.cpp
@@ -143,7 +143,7 @@ namespace test {
       verify_builder()
         {
           UICoord uic1 = UICoord::window("window");
-          UICoord uic2 = uic2.view("view");
+          UICoord uic2 = uic1.view("view");
           CHECK ("UI:window" == string(uic1));
           CHECK ("UI:window[*]-*.view" == string(uic2));
           CHECK (1 == uic1.size());
diff --git a/tests/library/path-array-test.cpp b/tests/library/path-array-test.cpp
index b4b88e97a..db129ef28 100644
--- a/tests/library/path-array-test.cpp
+++ b/tests/library/path-array-test.cpp
@@ -481,6 +481,16 @@ namespace test {
           CHECK (ParrT("" ,"Δ","Θ","Ξ","" ,"Ψ","Φ","" ) == ParrT("" ,"Δ","Θ","Ξ",nullptr,"Ψ","Φ"));
           CHECK (ParrT("" ,"Δ","Θ","Ξ","*","Ψ","Φ","" ) == ParrT("" ,"Δ","Θ","Ξ",nullptr,"Ψ","Φ"));
           CHECK (ParrT("" ,"Δ","Θ","Ξ","*","Ψ","Φ","" ) == ParrT("" ,"Δ","Θ","Ξ","", "Ψ","Φ"));
+          
+          ParrT src{"Γ","Δ","Θ","Ξ","Σ","Ψ","Φ","Ω"};
+          ParrT copy{src};
+          CHECK (not isnil(copy));
+          CHECK (src == copy);
+          
+          ParrT target {std::move (copy)};
+          CHECK (src == target);
+          CHECK (copy != target);
+          CHECK (copy != src);
         }
     };