I'd like to add the HTML file tag, 'file://', to be supported in ArcGIS Online and Web App Builder pop-ups.
Here is the why. My organization would like to have hyperlinks to a folder location. We've tested this by creating virtual directories and using a URL to access the files. It works fine when the link goes all the way to the file extension. However in a folder's case there is no file extension so it doesn't work. Just in a web browser (not using ArcGIS Online), entering a url (file://servername/folder/folder) to a virtual directory folder using the file call works, but since the file tag isn't supported in ArcGIS Online it doesn't work in any of our applications.
Here are the currently supported HTML tags: Supported HTML—ArcGIS Online Help | ArcGIS
Here is a post where I found the answer of needing the HTML file tag: Can a hyperlink to a local or shared folder be created in AGOL?