Just for posterity, I ran into the same problem as joshgel. My 1440p's highest "scaling:on" mode is "res:1920:1200 hz:60 color_depth:8 scaling:on". I tried that, but iStats Menu still reports the discrete graphics card using 19W, which is as high as before.
Given that the linked script just seems to create some sort of XML file in the right directory, maybe this is doable directly? I made an issue in the displayplacer Github to this effect: https://github.com/jakehilborn/displayplacer/issues/69
For those who come across this thread later, I found a reasonable solution that involves fewer hacks (at least to me). It still doesn't lower power usage below 18W with both displays open, but it's a cleaner version of the above solution. Here: https://github.com/jakehilborn/displayplacer/issues/69#issue...
what if `displayplacer list` doesn't show an option for my current resolution with "scaling:on"? does that mean my 16" MBP w 5500M doesn't support this resolution?
I'd love a solution that doesn't require closing the lid, as well.