Thank you for taking the time to evaluate Test Studio!
"I have certain tasks that will become part of a LOT of our tests. Logging in, entering notes on a standard window, etc."
This is precisely the reason we added our Test-as-step feature a long time ago. This allows you to modularize your tests, much like functions/subroutines of a software program. Use this feature to create smaller subtests that do just the individual task (logon, enter note, etc.) and then call that module from the parent test. Now if your login sequence changes or the note page changes, you have just one test to update it all the parent tests will automatically use the updated subtest.
There's also no technical limit on how deep you can go i.e. a subtest can call another subtest which can another subtest and so on. For practical reasons (being able to keep track of the design of your test project) it's a good idea to limit the number of levels to about 3. More than that and the complexity becomes more than most people (myself included) can keep track of.
I hope that answers your questions.
the Telerik team