I want to execute strategies only if daily delta of BTC is around zero and the market is in flat, what parameters can be used to do that?

You can set these conditions on the Filters tab of the strategy settings, using the following parameters:
Delta_BTC_24_Min=-0.2 (Minimal change of BTC exchange rate in 24 hours (in %), below which the bot will not consider a coin)
Delta_BTC_24_Max=0.2 (Maximum change of BTC exchange rate in 24 hours (as %), above which the bot will not consider a coin)
That is, if BTC’s delta for 24 hours will lie in the range from -0.2% to +0.2%, then it has low volatility, which corresponds to the “flat” mode.