Something like this has been asked years ago, but it was never conclusively answered (that would include a fuggedaboutit from the developer). And $SEARCHENGINE does not return any results.
How can I execute a two-finger left swipe in an action, at the current or at a to-be-set location?
For gestures and other potential triggers that aren't supported by KM (perhaps because they aren't revealed by the public APIs) take a look at Better Touch Tool. That isn't an "instead of Keyboard Maestro" -- they work happily together and you can trigger KM macros from BTT and vice versa.
Thanks for the pointer. I thought I'd do a keyboard trigger and then a trackpad action (two finger swipe left) associated with that. and I'd send the keyboard trigger from KM.
but... I only find 3finger swipes under "standard gestures", and only a post from 2018 that sending swipes programmatically is not possible. Is that still so, therefore the hint for BTT is a deadend?
Wearing my Security Officer hat -- If you've so many warnings in that pane that you need a macro to hide them then you should sort out the underlying problem(s) instead of sweeping them under the carpet with the "Hide" button. Especially true when it's leaked credentials that have also been used on other sites...
With my "official duties" done -- try right- or control-clicking on the item instead. That should bring up a "Hide Security Recommendation..." button for just that entry, which you can then click/press with another action.