Maybe this is of interest for you: I have drafted a function, mediation(), that prints a compact summary especially for mediation analysis (similar to the output from the mediation package).
You can see examples in a vignette here:
https://strengejacke.github.io/sjstats/articles/bayesian-statistics.html#summary-of-mediation-analysis
There’s a comparison of brms to the mediation package, and the results look good!
You need the current dev-version of sjstats to check out the mediation()-function.