Wait for second reboot in custom tasksequence
The docs say that SMSTSWaitForSecondReboot variable does not apply to custom task sequences. That is true, unfortunately.
A few customers use custom tasksequences to update application bundles and the variable could help here.
The problem: Software Updates (Cumulative W10 etc) have been installed during the day, reboot is pending until next maintenance window. Maintenance window opens at night and starts task sequence for application updates. Task sequence has a reboot step or app install forces a cm hard reboot by exit code 1641. Now when the system reboots, the task sequence may fail on startup because of a second reboot caused by update installation.
We actually see that problem with January updates causing four reboots on startup, two with about five minutes inbetween.
Current workarounds are
a) to either schedule a reboot (scheduled task) before the large maintenance window starts to finish update installation, or
b) split the maintenance window in a small one that fits for reboot and a larger that can run the TS.
I'd believe the variable could be more fail safe.