@run-out Ok thanks, that are good first steps I'll use.
The issue is that I would like to register those "pre-buys" with a price I choose. Or the value that will change overtime will be wrong.
For example : if I bought on my paper trading session 50 assets A for $100 in the past, I can't simulate this with your way. I'll be able to "pre-buy" 50 assets, but with the market price at the first bar. It would be amazing to "set_position" and "set_prices" of those positions manually, especially in a pre-next, to create a custom "starting state".
@vladisld I'm not sure about the difference between scenarios. I guess it's 1. Yes, 2. No, 3. Kinda.
I'd like to be able to create checkpoints to have a better "papertrading" behaviour on backtrader.
If I change my data, or my signals calculations today, I'll change all my past performance and decisions if I re-run backtrader with those changes.
I'd like to be able to do backtesting "step by step", keeping the past untouch even if I modify my code.
Those are two faces of the same coin.
I hope I'm clear now, and sorry for my English :)