Task with 50% max resource

Is there a way to create a Task that would only utilize 50% of any resource assigned?

In other words, I don’t necessarily want to finish the task early by having the resource work full time on it, I want that resource to work multiple Tasks simultaneously.

I don’t know of any way to mark a task so that all resources are automatically assigned a specific percentage of their time to work on it. You can, of course, mark each task resource individually as such and the timeline will be adjusted accordingly.