If you're trading intraday, my go to filters that seem to deliver constantly better results are : RVOL (RVOL average above 100% for example or RVOL value above average)
Relative ranges (same ideas as above). Although with this one you want to be careful as bearish Price action tends to correlate with high ranges. But at the same time you want to make sure there is enough meat on the bone if you take a trade intraday so double sided sword.
Daily IBS (internal bar strength) less than 0.25 (a bit too restrictive but can work) less than 0.5 (more general, making sure you're not entering on highs) for mean reversion, or greater than 0.75 / 0.5 if you want the filter to filter weakness.
I will also use decreasing ATR or increasing ATR for gaging volatility but to be honest Relative Range does that as well if not better.
Previous day red or previous day green is also a good simple one, and location of current candle relative to prior day OHLC is good as well.
I'm not a fan of "classic" filters such as under/over 200sma because they filter too much out.
If you want to take a breakout of the OR and you're filters tells you not to because it's under 200sma and the trades plays out super well you're essentially removing edge in your strategy. I don't like that
I prefer using filters to only (even though it's hard to master) filter out a broad, loose PA behavior that statistically will tend to decrease my edge.
I'm not trying to improve performance but rather decrease unperformance if that makes sense.
You might also consider using complementary strategies. It's the ultimate edge against a loosing trade. If you take an ORB and it fails, have a strategy that exploits failed ORB.
It's a better approach to take in my opinion
So many ways to ruin you're hard work when you use filters.