During backtesting, it seems that the enterLong() or enterShort() functions enter trades at the CLOSE of the next day (after a buy or sell signal was generated today by whatever strategy is used).
How can I enter a trade at the OPEN of the next day?

Thank you in advance! Any answer and/or example is highly appreciated, as I couldn't find anything in the manual or this forum.

Maybe you could run tick() once at the end of each bar? This will trigger the function upon the next incoming price tick (which should be the open of the new bar).