I'm a recent Windows to 2021 MacBook Pro convert. Not knowing it was impossible, I managed to stumble on a method using Disk Utility. - Launch Disk Utility - Erase the disk and create “Time Machine Backup” volume - Notice that no option to limit size is available. - Delete the Time Machine Backup volume just created. - Add a volume named Time Machine Backup and supply size constraints. - Add additional volumes with or without size constraints. - Launch Time Machine and Select Disk ->Time Machine Backup - Here's what I ended up with. Seems to work. [![Disk Utility][1]][1] [1]: https://i.sstatic.net/6qzqX.png