Thanks for reply. Yes I know, this only matters when printing the pictures, which doesn't happen very often these days, but it does happen from time to time. My idea was to have a standard resolution for images, so that 3 images of the same size in an article not come out with very different sizes on a printout.
Meanwhile, I've realized that my first question didn't reflect what I wanted to achieve, which was simply to set the resolution to 96 without changing the number of pixels for the image. A resampling is not required to change resolution, and changing resolution should not change the file size. Reference: “However, the PPI has no impact on the file size”:
https://nickkidd.net/blog/2020/7/21/72-ppi-is-a-myth
So if JCE removes the resampling option, maybe you could replace it with an option to just change the resolution without resampling?
The JCE option with resampling to 72 DPI seems to have a strange effect on file size. I uploaded an image of 4000 x 2667 pixels, resolution 300 PPI, and file size 2.04 MB, and then I end up with an image of 4000 x 2667 pixels, resolution 72 PPI, and file size 4.79 MB. Why is the file size changed when the number of pixels is the same as before, well not just changed but actually more than doubled?