Is there a way we can change the settings that when a new trade with bigger lot is initiated, it doesn't change the TP of the previous lower lot? Instead, the previous lower lot trade should be given a reasonable SL. Most of the time, the lower lot trades will eventually win the trade
Seems like you have no clue how martingale EA works. It is best to close trades as quickly as possible, and that's why the TP changed when a bigger lot is opened. All trades will close at the same time with an overall profit. That's the whole idea.
You are wrong to say that lower lot trades will eventually win. Trending markets happen all the time, and you may not even see the same price till a few weeks later.