如何从Android Studio中的索引删除目录?

我有一个很大的项目文件夹，其中包含许多子项目. Android项目只有4个，其余都是C代码.

I have a large project folder that contains many sub projects. Only 4 are part of the Android project, the rest are C code.

但是，似乎Android Studio正在为所有内容建立索引，这需要很长时间.

However, it appears that Android Studio is indexing ALL of it, which takes a long time.

如何从索引中排除其他目录?

How do I exclude these other directories from indexing?

无法明确地执行此操作，并且模块设置"仅列出了Android项目，因此我无法从此处删除其他文件夹.

There no way to explicitly do it, and the Module Settings only lists the Android projects so I cannot remove the other folders from there.