Adding the ability to save in Training Levels

[MysticaL-AceR]

I don't know how complexed this sounds to fix it but, the stock game doesn't let you save progress as you play through training levels.

And now with the establishment of new Singleplayer content, new mods may use custom training levels acting as prologues to campaigns themselves, that may require saving depending on how long they may be. Wouldn't it be nice to save/load in those levels too ?