Open with Explorer is a button, which gives users possibility to open a library in Explorer. It’s great while we just want to add or copy some content. However, the problem is while user drag and drop the files with folders in library it create a folder. In addition, folder we don’t like in SP.
So this feature disable to open a library in Explorer for all libraries in a site. See pictures below:
Also recommended to use Feature called “Disable New Folders” which is included in this solution.
Install and use: