Most stats will work like this and this should give you some of the information you do want. You can set PT4 to only show heads up data when playing heads up via the Number of Players Filtered area in the Hud -> Edit Hud Options window. That will be how often you made exactly a 4bet preflop when in the SB.
Use that and set it to the SB position by changing the Position drop down in the Item Properties area at the top right. You don't need to combine anything for this setup - the 4Bet Preflop stat will be sufficient.
