Würde das weniger kompliziert angehen:

1. nur Verbindungen betrachten
2. Anfang und Ende einer Verbindung als TreeItem merken
3. Optional*: Schema auf Sinnhaftigkeit / Fehler überprüfen
4. Optional: TreeItems in einer Liste zwischenspeichern; z.B. hilfreich wenn man die Schlüssel nach Typen des Teils wählt (z.B. alle Regelklappen) -> man kann direkt zum gew. Teil springen - ohne Namen zu kennen - und von da losrechnen
5. Optional: Sortierung der Liste z.B. nach Kantenlänge (Entfernung von einem Knoten zum Root-Knoten)

'#
'# Klassen-Modul: TreeItem
'#
Option Explicit 'non global or non modular variables used in Subs or funciton have to be declared by dim
 
Public Parent       As TreeItem
Public Shape        As Excel.Shape
Public LeftChild    As TreeItem 'pointer to the left child node
Public RightChild   As TreeItem 'pointer to the right child node

Public Property Get Name() As String
  Name = Shape.Name
End Property

Zum Testen:

Sub Test_Call()
  
  Dim objRoot As TreeItem
  Dim n As Long
  
  n = GetTree(Worksheets("Tabelle1"), objRoot)
  
  Debug.Print "root-element"; Tab(50); "'"; objRoot.Name; "'"
  Debug.Print "root-element::LeftChild"; Tab(50);: Debug.Print "'"; objRoot.LeftChild.Name; "'"
  Debug.Print "root-element::LeftChild::LeftChild"; Tab(50);: Debug.Print "'"; objRoot.LeftChild.LeftChild.Name; "'"; " (parent is '"; objRoot.LeftChild.LeftChild.Parent.Name; "')"
  
End Sub

... und das worums eigentlich geht:

'#
'# Modul: modTree
'#
' VBA-Editor:
'  Tools -> References:
'   * Microsoft Scripting Runtime
'
Option Explicit

Public Function GetTree(ByVal Worksheet As Excel.Worksheet, ByRef Root As TreeItem) As Long
  
  Dim dicTI As Scripting.Dictionary
  Dim shp As Excel.Shape
  
  Set dicTI = New Scripting.Dictionary
  
  For Each shp In Worksheet.Shapes
    If shp.Connector Then
      With shp.ConnectorFormat
        If .BeginConnected Then
          If Not dicTI.Exists(.BeginConnectedShape.Name) Then
            Set dicTI(.BeginConnectedShape.Name) = New TreeItem
            Set dicTI(.BeginConnectedShape.Name).Shape = .BeginConnectedShape
          End If
        End If
        If .EndConnected Then
          If Not dicTI.Exists(.EndConnectedShape.Name) Then
            Set dicTI(.EndConnectedShape.Name) = New TreeItem
            Set dicTI(.EndConnectedShape.Name).Shape = .EndConnectedShape
          End If
        End If
'        Debug.Print "# '"; .BeginConnectedShape.Name; "' is ";
        If dicTI(.EndConnectedShape.Name).LeftChild Is Nothing Then
'          Debug.Print "LEFT";
          Set dicTI(.EndConnectedShape.Name).LeftChild = dicTI(.BeginConnectedShape.Name)
        Else
'          Debug.Print "RIGHT";
          Set dicTI(.EndConnectedShape.Name).RightChild = dicTI(.BeginConnectedShape.Name)
        End If
'        Debug.Print " child of '"; .EndConnectedShape.Name; "'"
        If dicTI(.BeginConnectedShape.Name).Parent Is Nothing Then
          Set dicTI(.BeginConnectedShape.Name).Parent = dicTI(.EndConnectedShape.Name)
        End If
      End With
    End If
  Next
  
  Set Root = GetRoot(dicTI)
  GetTree = dicTI.Count
  
End Function

Private Function GetRoot(TreeItems As Scripting.Dictionary) As TreeItem
  Dim objItem As TreeItem
  Set objItem = TreeItems(TreeItems.Keys()(0))
  Do Until objItem.Parent Is Nothing
    Set objItem = objItem.Parent
  Loop
  Set GetRoot = objItem
End Function

LG