Hi there,
Thanks for following up with your feedback! At the moment, we don't have an immediate replacement for Rank Tracker in place, but as you mentioned we do have several places where you can check rankings. One would be in the Campaign, especially the Analyze a Keyword section which allows you to view the live SERP with the top 50 ranking sites. Another way to check live rankings is using Keyword Explorer. If you have a Keyword List there, you can check any URL for presence in the top 10 positions.
Another workaround for quick rankings gatherings would be to create a Campaign and add those keywords during setup. We'll do a quick rush collection and within a few hours you should see those results. You can then delete or archive that campaign if you no longer need it.
Apologies for any inconvenience caused by the removal of Rank Tracker. We have hopes to bring you better, faster, more accurate tools in the future (such as the brand new Link Explorer!), and we will certainly let the product team know that on-demand rank checking is high on your list.
Let us know if there's anything else we can do for you!