If someone knew personally a couple of good, switched on people running a small NGO on the ground (potentially EA adjacent people), my insinct would be to go for that as it will likely be more efficient and well targeted than later scale efforts

From my experience in the aid world, MSF do an amazing job of counterfactually providing medical care where noone else does or can. In difficult conflict situations I suspect their cost effectiveness may sometimes be surprisingly high as there are likely to be many people who would have died if they weren't there.

My instincts and prior research has pushed me away from most BINGOs (big international NGOs) like world vision, care international, save the children etc as they are inefficient generalists, without special expertise and are more inclined to follow the whims of donor money with their work rather than double down on their competitive advantage or high impact work on the margins. I don't see why this would be different in a warzone.

GiveWell's previously recommended MSF as a good disaster relief org, so that would be my best guess. I'd love to know more, though.  

Charity Navigator has published a list of trustworthy, disaster relief organizations working in the area: https://www.charitynavigator.org/discover-charities/where-to-give/israel-hamas-conflict/

They only evaluated one organization for impact and gave it a perfect score, but don't show their work: https://www.charitynavigator.org/ein/453782061

Knowing nothing else, you could select a few promising orgs from that bucket, but I wouldn't give them the label of being "highly effective". Maybe the best thing to do is even to support groups in Israel that advocate for a more humanitarian military response.