Hi Leo,

There are several helpful resources that I find for drag/drop.

Ext 3.4: http://dev.sencha.com/deploy/ext-3.4.0/examples/#sample-14
Ext 4.0: http://dev.sencha.com/deploy/ext-4.0.1/examples/#sample-9
Saki (Ext 3.4) : http://examples.extjs.eu/

I think I know what you are describing, but we do not have an example of implementing panels that move on drag-over in LabKey. We implement drag/drop in the tree panel, which is going to be pretty different from what you are looking to build, but it could help. Search for FolderManagementPanel.js in our core/webapp/admin folder.

Thanks,
Nick