As an Admin, the "Log In As User" function (in the Setup section) is probably my most used feature--yet it's so buried, it's not as useful as it could be.
A few ideas that I'd love Workfront to implement to make this well-loved feature even more useful:
Ability to "Pin" the "Log in as" to the top navigation bar (in the New Experience)
Ability to easily switch between users (so you don't have to log out of one user, go back into Setup and then log in as a new user)--I'd envision a button right next to the orange "Log Out" box that says "Switch User"
Log in as 2 users at once (to get side-by-side views of each user and troubleshoot potential problems)