Hello! My name is*****
I am a certified computer professional who will assist you with the problem you described.
Since it seems you still require assistance with the "line spacing" problem, and none of the Experts have provided a helpful answer, let me explain what has most likely happened and how to fix it.
WordPerfect comes with several different menus you can use. That allows you to change or customize the menus if you don't like the default one. You can also switch to a Microsoft Word style menu. So, it looks like you have accidentally changed to another menu, which would explain why you don't see the Line Spacing appeared under Format > Line > Spacing...
To fix the problem, you need to select the default WordPerfect menu. Here are the instructions on how to do that:
1. Start WordPerfect
2. Click on Tools and then Settings...
3. On the Settings window, click on Customize
4. Click on the Menus tab
5. You will see the menu that is currently active. The default menu for WordPerfect 8 is the one called <WordPerfect 8 Menu>. Click on it and then click on the Select button on the right
6. Now click Close twice to exit the windows. Since the default menu has now been loaded, you should be able to access the line spacing by clicking on Format > Line > Spacing...
In case you still don't see it, you can load another menu, such as <WordPerfect Menu> or you can reset the menu to default settings. Do that by clicking on the name of the menu and then click on the Reset button.
I hope this helps! If there is anything else I can help you with, let me know.