Working with PowerDesigner models through VB interface

PowerDesigner has great automation abilities. The easiest way to work with a model programmatically is to use PowerDesigner's embedded Visual Basic script interface and to run scripts through 'Edit/Run script' window.
Here's an example script that uses given color to highlight tables that have comments or that have at least one column with a comment:

Dim model
Set model = ActiveModel
For each table in model.Tables
   doPaint = false
   tableComment = Trim( table.Comment )
   if ( "" <> tableComment ) then
      doPaint = true
   end if

   if ( not doPaint ) then
      For each column in table.Columns
         comment = Trim( column.Comment )
         if ( "" <> comment ) then
            doPaint = true
            Exit For
         end if
      Next   
   end if
   
   if ( doPaint ) then
      For each symbol in table.Symbols
         symbol.BrushStyle = 6 'Gradient 
         symbol.GradientFillMode = 64
         symbol.FillColor = RGB( 252, 178, 104 ) 
         symbol.GradientEndColor = RGB( 255, 255, 255 )
      Next
   end if
Next

More info about PowerDesigner automation at SyBooks and PowerDesigner's 'Metadata Objects' help file.
Tip: when reverse engineering big unfamiliar scheme you can easily select and move apart particular symbols by adjusting their 'Position' property. For example you can select and move tables with particular prefix:

Dim model
Set model = ActiveModel
PREFIX = "hh_"
For each table in model.Tables
   tableName = LCase( Trim( table.Name ) )
   if ( PREFIX = Left( tableName, Len( prefix) ) ) then
      For each symbol in table.Symbols
         symbol.Position = NewPoint( 0, 0 )
      Next
   end if
Next

After desired symbols are moved to the (0,0) position they can be selected and arranged with 'Symbol->Auto layout command'.
This simple solution of how to distill big scheme came to me after I had reversed database with 2K of tables with a few foreign key constants defined. I faced a brick wall of tables arranged by their column count. All semantics were encoded in table names so I just had to set apart tables with equal prefixes. I've searched for a function to add symbols to selection but with no success. So I decided to move desired symbols to the center of workspace and then to select them with single mouse movement. That's when 'Auto layout' command came in very handy.