I'm using DAC Cosine Wave Output (Cosine Mode). But!!! when using cosine wave frequency of 150Hz -- ADC Continuous Mode Driver with sampling rate of 30kHz detects Cosine Wave period with ~100 samples (300Hz); when using cosine wave frequency of 10kHz -- ADC Continuous Mode Driver with sampling rate ...

struct adc_continuous_handle_cfg_t have
uint32_t flush_pool
Flush the internal pool when the pool is full.
member adc_continuous_handle_cfg_t::flags : set the flags that can change the driver's behavior. flush_pool: auto flush the pool when it's full. ( https://docs.espressif.com/projects/esp ...

does this need to be done?

You shouldn't have to filter every single sample though, because they should come alternating between the channels. So if result[x].channel == channelX, then channelX results should all be found in result[x + pattern_num * i] for i >= 0.

I can't find such a ...

the documentation does not provide information about the order in case of a configuration with several ADC channels (Continuous Mode).
https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/peripherals/adc_continuous.html#driver-concepts

i use ADC with 2 number of the channels ...