# Formulating mutli-membership random effects in lme4/GAMM4

I'm trying to fit a GAM with multi-membership random effects and nested effects in the package GAMM4, which uses lme4 syntax. Does anyone have any experience doing this in either package? Is it possible, or are we restricted to using another package?

An equivalent model in BRMS has the following notation, with the mm() function:

brm(<response> ~ <fixed effects> +
(1 + mmc(Effect1, Effect2) | mm(Group1, Group2)),
data = data,
family = bernoulli())