If you are brewing a single-turn batch, but the capacity of this batch is greater than your fermentation vessel capacity, and you, therefore, would like to split the batch across two fermenters, then you will need to first move this into a large holding vessel. This vessel does not need to represent an actual vessel in your brewery and is just for the purpose of transferring a single batch into multiple vessels. Once the full volume has been transferred to the large holding vessel, you will be able to transfer your batch into the correct smaller fermenters.
Our Setting up your brewing system and vessels help article will guide you through creating a holding tank in Breww. Once you have created your holding tank, that’s volume is great enough to hold the full volume of the batch; you can transfer the batch into the correct smaller vessels.