The only reason you would need to find a task status ID is to use it through Zapier.
At the moment we don't present the task status ID's anywhere in Project.co but we doi display them in Zapier.
So, to find the task status ID click into the task status input and you'll see your task statuses listed. Underneath each stask status name is it's ID:
So for example Active has an ID of "5" and Completed has an ID of "6".