Ext.ux.grid.FormEditor is an extension of Ext.grid.CellEditor that attaches a floating Ext.form.Panel to the cell editor's field.
For a live example, check out the Fiddle: https://fiddle.sencha.com/#fiddle/1ao
The form can be configured with any fields desired, and its alignment to the cell can be configured via the Ext.Component#defaultAlign property. The form will be "saved" when the Editor completes its edit. By default, the fields will be saved directly to the edited row's underlying Ext.data.Model instance by calling Ext.form.Panel#updateRecord.
This behavior can be customized by configuring the FormEditor with overrides for #loadForm and #saveForm.