Setting safe mode for the next reboot has become quite tricky.
Usually, you have to navigate among one-way system options (reset, restore, …).
Recently I discovered that you can easily trigger it from Command Prompt with administrator access rights.
Type the following command:
bcdedit /set {default} safeboot minimal
and reboot.
The system will reboot in safe mode as requested this time only.
If it will not switch back to normal mode by itself, you can help it by this other command:
bcdedit /deletevalue {default} safeboot
and reboot again.