I would run an update macro if you have existing data to indent, just the range then run (in a normal module). Obviously this can be updated/improved
Code:
Sub IndentArrows()
Dim r As Range
Dim c As Range
Set r = Selection
For Each c In r
If Left(c.Value, 1) = ">" And c.IndentLevel = 0 Then c.InsertIndent 1
Next c
End Sub