My Group Content is getting very cluttered -- lots of layers and maps. Is there a way to create folders and sub-folders to manage things? I'm thinking there is and it's pretty simple. I just can't find it.
You cannot create folders within your groups. You are able to sort your content in a group on ArcGIS Online and you can also filter your content with our Admin Tools for ArcGIS Online. This is something you will have to contact Esri for, they have an ideas page where you can post an idea & also see ideas from others within the community. https://c.na9.visual.force.com/apex/ideaHome?sfdc.tabName=01r30000000dxas
