How do I know which sheets are to the RIGHT and LEFT to the Active Sheet?

You could assign these two macros to shortcut keys (i.e. Ctrl+b and Ctrl+f ) so you could key your way thru the various sheets. You could also have a "Ctrl + i" that would activate the "index" sheet.

Public Sub forward()
   On Error GoTo FirstSh
   Sheets(ActiveSheet.Index + 1).Activate
   Exit Sub
FirstSh:
    Sheets(1).Activate
End Sub

Public Sub backward()
   On Error GoTo LastSh
   Sheets(ActiveSheet.Index - 1).Activate
   Exit Sub
LastSh:
    Sheets(Sheets.Count).Activate
End Sub