We have a process outside of Appian that launches a user into Appian and routes

That's correct. This is the default behavior; when a task is completed you are redirected to the My Tasks list if there's no other context (e.g. if you didn't launch the task from a dashboard)

We are launching the task thru a simplepopu url. I'll paste the url below and attach a screen of the task once user submits/or ends task. The problem is the task does comple but screen continues to say "Working" and a browswer popup is displayed asking if you want to close this tab. If you say "yes" on popup all windows close, which is what we want. How do we get rid of the popup and why does it say "Working" when it's not.
url: xxxxxxxx:8080/.../getTaskDetails.simplepopup
Thanks! and please see attachment which shows the behavior when user clicks submit button.

Oh I see, that's the expected behavior. You better use /suite/task/xxxx instead.

That does close the task window, but then the task list windows opens, which displays all My Task. What we are trying to do is only run the task and not redirect user back to a task list, which they were never at in the first place. Is there a way to prevent this? Thansk!

The modern UI allows you to do something like that forum.appian.com/.../Embedding_Appian_Interfaces_in_External_Sites.html

Unfortunately that want work for us because we are on release 7.2. Any other options?
Thanks!