The XDA Forums always has some good content to check out, especially if you're into modding your Android device using ROMs. However, a user has figured out a way to swap out his SSHD in his Nvidia Shield Android TV Pro with that of another new SSD. The Pro version already comes with 500GB of storage, but if you want to increase that, or put in a replacement SSD or another reason, then you can do it now.
Before you jump into this though, the guide the XDA user Tilator already assumes you know how to open up your Nvidia Shield Android TV unit, how to detach the existing SSHD, how to put in this new SSD, and that you have a PC running Linux with a free SATA port available to use. So his guide is more from preparing the new SSD you want to use so that when you install it into your Shield Android TV unit, you're ready to go.
We won't post the guide here, so you'll be able to check it out over on the XDA Forums. However, the guide is only a few steps so if you have some technical know-how and experience with Linux, you should be able to do this swap in very little time with very little effort. If you're interested in doing this, head over to the XDA Forums to check out the guide.