I know I can put them in seperate files, but I think maybe they could be put in one file and I can use them seperately in unity editor. The reason I want to put them into one file is because they are related and most of them (except the main script) are very small, just record some datas or hold serval gameobjects. If I can put them in one script file would be convenient.
You can add as many monobehaviours in one file as you like if you use this workaround: https://forum.unity.com/threads/2-smaller-scripts-vs-one-large-script.697814/page-2#post-4706921
Otherwise you can only have one monobehaviour per file.
EDIT 1: You can actually use AddComponentMenu() now, which is much easier than the method I suggested.