I don't want to discourage people from doing that 1-click thing, but you need to be realistic about what it it accomplishes. By their own count in Quarter 4 of 2023 (October to December) they had over 500,000 clicks, which led to a donation of a little over $380 USD to UNRWA.
That's far from nothing considering the cost to the clickers being almost nil, but you'll have a significantly larger impact if you personally donated $5 to UNRWA yourself, and if you're in the US you can even make that tax-deductible!
I should note that the ban on directly funding UNRWA might come into play but for the moment you can still donate directly to the organization or UNRWA USA which will send most of the money to UNRWA as a grant while using some of it for stateside advocacy.
Keep clicking, but if you have even a few dollars to spare you can have an even larger and more direct impact, while diverting at least a few cents away from Biden's bombs.