It would depend on the exact nature of the scenario you are posting. If it is just a single mission then YES you would have to ether use a mod loading tool that adds the info to the text.utf8 and Campaigns.xml files for you in the SINGLE_MISSIONS folder, or go in and add them manually.
(Change the file extensions to .txt to edit)
Now if you are doing as you stated and are making a whole new campaign like that of the Panzer Lehr Campaign that has a whole list of missions that run consecutively one after the other. Well then just copy the file structure from Panzer Lehr and rename everything so there are no compliance issues.
If the game dosn't read the new files in the new campaign sub folder, go into the mission-campaign editor and open the first mission. In the mission tree it will show the name of the mission file. (the senerio for that map)click on it.
Now in the properties window it will show the name again and below that it says Campaign. If its blank or says Single_Missions, change it to reflect the new campaign folder you have the files in. This should correct the game not reading the files in the new subfolder for your mission/campaign.
I have found over the last two days that many ppl are stating there needs wrongly,
A mission is one battle!
A Mission set is a concurently runing set of battles!
A Campaign is ether a group of missions or a detailed group of mission sets that evoles from multiple concurently running scenarios.
I am not yelling at you about anything, its just I am having a hard time reading some of these posts and understanding exactly what ppl are asking for or about.
Ppl need to learn to proof read there posts before asking questions that just cause others to ask more questions.
Again I am not yelling at you. I am just trying to be sure I have the same though as to what you need answered.
UB
Oh P.S.
If you manuelly edit the files and go in the game and now see nothing listed, dont start pulling out hairs. Just go back out and change the files types back too .utf8 and .xml
I closed and opened the game three time before I realise I had forgoten to switch one of the files back.