This seems like a good time to try out my shiny new ZFS memory usage boilerplate message.
23.01 can appear to use more memory than expected if you are using ZFS for a few different reasons:
ZFS ARC (Adaptive Replacement Cache) usage is reported differently, though the behavior is similar to older versions #14011. ZFS will give up this cache memory as needed but not always fast enough for certain workloads.
To correct the memory reporting on graphs and the dashboard, install the System Patches package and then create an entry for 0d83ed084a987f3446a0cbdcf249fc5b8722726f to apply the fix.
The first boot after upgrading the ARC usage will be high from all the disk activity during the upgrade. This will gradually lower, or a reboot will make it go back to "normal".
FreeBSD default cron jobs are enabled when they shouldn't be #14016, and run at 3am causing RAM usage from ARC to jump overnight.
To correct this, install the System Patches package and then create an entry for ff715efce5e6c65b3d49dc2da7e1bdc437ecbf12 to apply the fix.
To set limits on ZFS ARC size to reduce the chance of contention for RAM, configure a tunable for vfs.zfs.arc.max to set a limit on how many bytes it can consume, e.g. 67108864 would set a 64MB limit. Also consider setting a "Free Target". Both are explained in detail on https://docs.netgate.com/pfsense/en/latest/hardware/tune-zfs.html.
A reboot is required to fully activate the changes from these patches. The ZFS ARC limit will take effect immediately but the wired memory may not be immediately freed, so a reboot is helpful for that as well.