Simply 3 different VWAPs for the pre-market, regular trading session, and the after hours, using session.is_ variables (not sure if they were recently added. Regardless, it would be nice to have a session.isfirstbar_postmarket variable to avoid having to write the code for calculating VWAP instead of simply using a ta.vwap function). Treats all 3 sections of the day as separate sessions with their own characteristics i.e. differing levels of liquidity and market dynamics. I would argue this is better than just using a VWAP calculated from the pre-market open until after hours close, as it would make using the VWAPs as a benchmark more accurate when taking trades at these different periods of the day.