猫鼬不能推到深层嵌套的文件多位置操作符

I want to push element to subfeatures nested document by using $push. but when i use like this ''modules.$.features.$.subFeatures'' it gives me the multiple positional operator error. so I get the features document index as x but i cannot figure out which way I can append that value to the query. 'modules.$.features.x.subFeatures' doesn't working.I want to push element to subfeatures nested do