Map Mavin now supports the uploading of layers directly into folders. To do so, click Create Layers in the Layers tab of the Admin Panel. In the following pop-up check the box titled "Save layer(s) to Folder". 

For the cancelling of uploads, simply click the X next to the name of the layer in the Notifications pop-up in the bottom right of your screen that shows a given layer in the processing of uploading.