Power plans disappeared after Windows 10 Fall update (1709)

If you right-click on the battery symbol in Systray and start Mobility Center you can still se three power plans in the combo box and select one.

Answer copied from: Can't change powerplan settings in Windows 10 build v1709

The powersettings dialog itself has not been changed, but the upgrade removed all powerplan settings but the Balanced one, and it will remember the setting currently in use.

If you switch to the balanced one, your old one will be forgotten too.

In order to get them back, you need to create a new powerplan first, mark one of the 3 templates and give them a name. For example, if you want to use the default High Performance powerplan, you first have to create it before you can switch to it.

https://answers.microsoft.com/en-us/windows/forum/windows_10-other_settings-winpc/only-1-default-power-plan-windows-10/2d9463d7-3be4-46a4-a902-b13a125520f6:

Open the registry editor. If you don't know how, open search/Cortana and type regedit.

Using the folders on the left hand side, navigate to the following folder: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power on the right, one of the keys near the top should be called CsEnabled. Click on this.

Change the value of this key from 1 to 0.

After you reboot you should have your power plans back. Hope this helps!

1. Open a command prompt.

2. Copy and paste the command below for the missing power plan you want to restore into the command prompt, and press Enter.

(Power saver)
powercfg -duplicatescheme a1841308-3541-4fab-bc81-f71556f20b4a

(Balanced)
powercfg -duplicatescheme 381b4222-f694-41f0-9685-ff5bb260df2e

(High Performance)
powercfg -duplicatescheme 8c5e7fda-e8bf-4a96-9a85-a6e23a8c635c

(Ultimate Performance - Windows 10 build 17101 and later)
powercfg -duplicatescheme e9a42b02-d5df-448d-aa00-03f14749eb61

3. You can now close the command prompt if you like.

Source: https://www.tenforums.com/tutorials/110372-restore-missing-default-power-plans-windows-10-a.html