In order to get the Pro & Bonus tracks to appear in the Solo Campaign, go to the Resources and download the Tool: https://www.speedrun.com/tools/Pro_and_Bonus_Campaign_9izx0.zip
In this downloaded folder you will find edited versions of a Nations folder and a Solo folder.
Go to C:\Program Files (x86)\TrackMania Nations ESWC\GameData\Tracks\Challenges\Nadeo\Nations
Go to C:\Program Files (x86)\TrackMania Nations ESWC\GameData\Tracks\MatchSettings\Solo
The Pro and Bonus tracks should now appear in the Solo Campaign.