Shopify Flow

Can be somewhat convoluted and confusing at first; once you get the hang of it, it can be extremely useful. Plus this app has only gotten better as the devs continue to add new values, actions, and conditions. I use it to add order tags, send internal emails, send customer emails, customer notifications (abandoned cart, abandoned browse), and various other operations that I wish to run in the background automatically. It takes a lot of manual work off my plate and keeps my physical workflow easy and simplified.