TextRange.InsertAfter (PowerPoint)

Appends a string to the end of the specified text range. Returns a TextRange object that represents the appended text. When used without an argument, this method returns a zero-length string at the end of the specified range.

InsertAfter (NewText)

NewText: The text to be inserted. The default value is an empty string.

Dim treInsertAfter As TextRange
Set treInsertAfter = ActivePresentation.Slides(1).Shapes(1).TextFrame.TextRange.InsertAfter()