Wow this is a long article name. But it’s appropriate!
This message can be seen throughout the Line Editor screen and/or the Documentation Generator screen. The above screen cap shows Quote Line Group as the culprit. But there are common others such as, but not limited to: Quote Line, Product Option, and Product Feature.
What does this message mean???
It means you used to have a tab for that object but now do not. You need to create a Custom Tab for the object in question. You see, objects that do not have a tab also do not have a ‘LastViewedDate’. And for some reason, when the tab is created, CPQ takes note of it and never forgets, even when you remove the tab.
Create the tab. Try again.