When running the Analyze area tool from Area Editor, if the area is large enough to be partially outside of render distance, it will display the "Scheduled task added" message and show a HUD with all the unseen chunks.
The problem is that, after emptying the list of missing chunks by visiting them, when you go back to the Area Editor and click Analyze Area again, it will schedule a new analysis instead of showing the results of the previous one, so it won't allow you to use that tab.

Minecraft Version: 1.15.2
Litematica Version: 0.0.0-dev.20200409.182607
Fabric Version: 0.7.8_build.189

The result is viewable in the Material List. You would have to open the material list using the hotkey in this case, because otherwise the material list instance would get changed to that of the placement if you try to open it via a placement configuration menu. This is pretty clunky way of using it, and it's among the things that will get improved when I do a bunch of other material list related changes and improvements at some point soon.