Missing Power Plans
Fix power plans that are missing from your system.
Modern Standby
You can try to disable something called *modern standby* by searching in your search bar for the registry editor and then making your way to this file path
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power
Once you're inside of here, search for PlatformAoAcOverride and set it to a value of 0. If you do not have this value naturally in your registry editor; right click and create a new dword 32 bit value and name it exactly as PlatformAoAcOverride
Restart your machine and check again for your power plans
Brief rundown on modern standby:
Modern standby is a 'low power idle mode' typically used in laptops/tablets. It replaces the older S3 sleep state to this new modern standby with an "always on, always connected" behavior, similar to how a smartphone can sleep but stays connected. When you disable modern standby... S3 sleep becomes available, which will affect the features you once had from modern standby like fast resume and potenially sleep funcitonality will be altered too, either taking longer to wake up without modern standby, or not being able to sleep at all. The reason why disabling modern standby can fix hidden power plans is because modern standby assumes the system will manage power automatically, so it hides most advanced power options which includes some power plans. disabling gives full control back to you, the user. If after all of this if it still doesn't appear, ensure there are no errors in the way you are importing your plan, as these methods should work for anyone in importing a power plan.
Option 2
You may be able to reset power plans with this command, start by opening Command Prompt as an admin, then paste in this code
Powercfg -restoredefaultschemes
Option 3
If you've disabled any services in relation to power, it may also cause issues. Ensure services like the Power service aren't disabled
Option 4
Ensure you are importing plans properly (if adding custom plans)
Last Option
You can check if the plans are actually importing and just not showing by typing this command into command prompt
powercfg -list
Doing this should show you a list of all powerplans imported onto your system (thanks to kye in my discord for the picture example)
If you happen to see that you have multiple power schemes without any names then take note of how many are in your list and then try to import your plan again; after another import type in powercfg -list again and see if a new scheme appears without a name
If you do happen to see a new scheme added without a name, copy the guid and then perform this command
powercfg -changename pasteguidhere "useanynamehere"
Once a name has been given to the previously unnamed scheme it should appear within your control panel now for choosing.