Unfortunately, that's not possible, but we will consider adding such option in the future and you're welcome to request it in our Votebox: https://todoist.com/Vote/
The votebox seems to be shut down.
Allow me to come back to the filter by assignee:
I think this is a very useful tool, when a supervisor wants to have an overview of the workload of one of his teammates, and it helps assist the meetings when they are one-to-one with each assignee. This is a tool that we find in the most todo applications, and I believe (with the bit of programming background I have) that it is easy to implement. Please make sure that our voice and request is duly conveyed to the relevant persons in your organization to make sure that this tool is implemented in the next software revision because I think this is the biggest shortfall of this software.