I’m sorry, but I have no idea how Google Tasks work, as I’m not using this integration. 
If you can provide more information, I’m sure we could get you started!
You could take a look at the recently changed behaviour of weather forecasts. There are some good examples out there, on how to setup a trigger based template sensor in combination with a service, what would be kind of a template for what you need to use for the todo list. 
But, as this has nothing to do with timer-bar-card, we should talk about that in a different thread. Please take a look at the search, if some other thread fits, or just open a new one! 