The “Quick Actons” widget disappeared from my phone this morning. I no longer see an option to add it, though I do see temperature widgets (in the classic style and the new iOS widget style). Was this widget removed from the app?
The only reason I installed Hue Essentials was because Philips removed the widgets from their app. It’ll be disappointed if this app fails me too.
Same here. It took them 5 years to add a home widget and when they do, the only useful application got removed 
New iOS 14 widgets and Siri Shortcuts were added recently in Hue Essentials 1.17.0. At the moment there is a temperature widget available and you can add Siri Shortcuts widgets for actions like toggling lights or activating scenes.
See for more information: How can I add widgets to my Home screen?
See also how to create Siri Shortcuts (which can be added as widgets on the Home screen): How do I use Siri Shortcuts?
Due to limitations in the new iOS 14 widgets they must open the app when clicked. That would not work very well for action widgets. Widgets through Siri Shortcuts do not open the app. So now you need to use Siri Shortcuts for action widgets.
Note that you can still add the old widgets (see Old Today View widgets under the first link). However, I cannot guarantee that they will be available in future iOS versions if Apple decides to remove them. All functionality of the old widgets is now available in the new widgets and Siri Shortcuts.
If you are still missing something or have any questions, please let me know.
Can’t seem to get shortcuts working. I keep getting “There was a problem running the shortcut” error. Using iOS 15 with latest update
Do you have the premium version of Hue Essentials? What type of bridge and lights are you using?
I have the premium version, using Bluetooth Hue lights.