Yea easiest way I can think:
I see audio on that drum track so just add the flanger you want to the track
1. Click the envelopes button on the track (yours might look different) and set the bypass of the flanger effect to visible.
2. Double click between markers 9 & 10 to set the time selection.
3. Make sure the effect is disabled and then drag the envelope inside the time selection to the level you want.