Windows – tell Windows 10 – ‘If I close the lid on the laptop, go to sleep IF I don’t have an external monitor attached’

By default, most laptops will go to sleep when you close the lid.

1. Click the Start (Windows) button
2. type "Power Options" and press enter
3. In the left hand pane, click "Choose what closing the lid does"
4. Under "When I close the lid:" select "Do nothing" (you can do this for on battery, plugged in, or both)
5. Click "Save Changes"

Now when you close the lid, your laptop should keep running and should recognize that only the external display is available.

You may want to read the whole power management guide, but the section about acpid is exactly what you are looking for. On my system I have:

# cat /etc/acpi/events/lid
event=button[ /]lid
action=/etc/acpi/actions/lid_down.sh %e

# cat /etc/acpi/actions/lid_down.sh
#!/bin/bash

#mute alsa.
#amixer sset PCM 0

#echo $*

dec=`echo ibase=16\; ${4^^}|bc`

if [ $(($dec % 2 )) -eq 1 ]
then
        logger "lid down"
else
        logger "lid up"
fi

If I wanted to suspend, I'd call hibernate-ram (tuxonice) instead of logging "lid down". I think the same thing can be done in Fedora with the pm-suspend command. If you find that this command does nothing, then it's likely a driver issue. You will have to research how to properly configure ACPI on that laptop.