It was impossible to adjust the built-in "sar" function so I implemented PSAR from scratch. So if you're interested in how it's work inside you can check the code and probably adjust to your need if you have a custom modification of PSAR in your mind.
you can try something like this:
strategy.entry("Long", true, when = trend_dir == 1 and trend_dir == 1 and trend_dir == 1)
strategy.entry("Short", false, when = trend_dir == -1 and trend_dir == -1 and trend_dir == -1)