Hello,

I suggest adding the parametric confidence interval around the eta squared effect size to the library pingouin.compute_esci.

There is a method to calculate it, based on the confidence limits for non-central F parameters. Here are some papers about it:
http://www.ww.w.statpower.net/Steiger%20Biblio/Steiger04.pdf
https://link.springer.com/article/10.3758/s13428-012-0228-7

This method is implemented in the MBESS package in R (conf.limits.ncf() function):
https://cran.r-project.org/web//packages/MBESS/MBESS.pdf
In Python, the function scipy.stats.ncf() could be of help to do it.

Thanks,

Federico