@whuber has demonstrated how to simulate multivariate outcomessimulate multivariate outcomes ($y_1$, $y_2$, and $y_3$) for one time point.
As we know, longitudinal data often occur in medical studies. My question is how to simulate repeated measures multivariate outcomes in R? For example, we repeatedly measure $y_1$, $y_2$, and $y_3$ at 5 various time points for two different treatment groups.