Haven’t tested this but a method that might be helpful in your scenario could be creating a custom Smallcase for the short-term trades. As Smallcase doesn’t follow the FIFO method for calculating average buy price (explained in detail here) it would likely show accurate P/L for those short-term trades.
But there might be some downsides like the inability to invest in a single stock when creating a custom smallcase (this can likely be mitigated by selling individual stocks later as explained here. Maybe @vasanthkamath could clarify this). Also, there is a one-time charge for creating a custom Smallcase.
To add to my reply above, the Smallcase method (if it works), would only show accurate P/L on its interface. Behind the scenes (aka on Kite/Console), you will continue to see what you are seeing now. This happens because the average buy price is calculated on a FIFO basis (explained here).
There was a recent discussion on a different thread about locking-in specific shares but that doesn’t seem to be possible -