Looks like we can't reproduce the issue or there's a problem in the test case provided.
am following your help guide on the designer (build 288) and touch (both beta versions) and have come to the part on adding a combo....where is it?
Can't find it in any of the tools sections of the toolbox?
Sencha - Architect Dev Team
Type "Combo" into the toolbox filter and it will show the combobox component when using the Ext 4.x framework.
Type "Select" into the toolbox filter for Sencha Touch and it will show the select field.
Sencha Architect Development Team
Should be under Forms and Views category as well