Possibly a better idea, but still stretching the limits of human engineering, would be to try to structurally reinforce the weakest points of Greenland/Antartic

Possibly a better idea, but still stretching the limits of human engineering, would be to try to structurally reinforce the weakest points of Greenland/Antartica, e.g. Jakobshavn, Thwaites, etc. It's important to understand these aren't just homogenous sheets of ice, due to geology/ocean currents/etc there's specific weak points that are collapsing far more rapidly, and as they do it will be like popping the cork off a bottle. If we could find a way to buttress the corks, it could help slow the melt-out. That said, any time you consider any geoengineering idea, you have to make the argument that the $1 trillion or whatever you'd spend on solar radiation management or ice shelf preservation or whatever, would not be money better spent on just transitioning away from fossil fuel use.