I have battled this for over 4 hours now. I am trying to use the assistant editor to open the class file for my tableviewcell. I have create the tableviewcontroller and its class file. I have assigned the class file as a custom class. I created a class file for the tableviewcell and assigned it as well. When I open the assistant editor and click on Automatic, I only have one item. I have: done a clean build - no help done a build - no help I have closed my project, reopened it, done a clean build - no help I have close Xcode, restarted my project, done a clean build - no help I have rebooted my system, restarted my project, done clean build - no help I have upgraded to Xcode 12.2, done all of the above - no help Once upon a time I had this working and I tried to think what might be messing things up. So I started experimenting. I had a basic test project in which I created the tableviewcontroller components and lo and behold, it worked. I then tried a test project where I used cocoapods to add some code to the project. I started the xcworkspace and created the tableviewcontroller components. This worked as well. So there was only one thing different with my non-working project. While it did have code added to the project using cocoapods, I also decided (on a whim) to us the Swift Package Manager to add GRDB to my project. I used the Swift Package Manager to add GRDB to my test project. After doing this, when I created a new tableviewcontroller and its components, I was not able to access the tableviewcell class file via the Assistant editor. This was only one test and it could be a fluke. It could be something between GRDB and the Swift Package Manager installation that would not show up when installing other packages. I don't care to find out. Now I can access the tableviewcell class file using the Assistant editor. That is the good new. But since I upgraded Xcode to 12.2, it is using the Swift 5.3.1 compiler and it cannot import GRDB which was compiled with Swift 5.3. So now my entire project is hosed until I can figure out a way to downgrade Xcode.
Maybe this will help someone else not waste a multitude of hours.