I just noticed I have the same problem. When I look at the "User Plugins" dialog window in the main program, I see that the plug is in the "Not Installed" list. But when I open the editor, I see that the plug is available (and works) under the "Plugins" menu.
Try this:
- Select a book in the main Calibre program
- Open the editor by clicking on the "Edit book" icon
- Click on the "Plugins" menu item in the editor
Check if there is an entry called "Convert Chinese Text Simplified/Traditional".
It's possible that the plugin is actually installed, but not properly registering with the main library application. Let me know what happens.
Edit:
Also, try this in the main Calibre window:
- Click on the "Preferences" icon
- Click on the "Plugins" icon which is at the bottom of the newly opened "Preferences" dialog
- Click on the "Edit Book Tool plugins" pull-down arrow
The plugin shows up in the list in this dialog in my case.