In [`limma::removeBatchEffect()`](https://rdrr.io/bioc/limma/man/removeBatchEffect.html) there is an option to add columns that should be included in the adjusting model, but not adjusted for. - This requires that all variables are are adjusted for are centered (continuous with `center()`; factors with `contr.sum`). - Then the coefficients for the non-adjusted variables are set to 0 before adjusting.