Check in cell background design property of transparent container element, any one of the design matches according to your layout design. IMO i think there is no specific design for a border in transparent container.
Workaround: Create a group -> design property - SAP color- looks like a border (you can make the header part as invisible)
There is a work around for your requirement.Wrap your group inside a group again and change the design properrty. You will get a clear visible border.
Here in the given screenshot i have made the design of outer Group to be Sap Color and made the group headers invisible using the visibility property of the Group Header. The inner Group design property is default.
Its not very clear in the screenshot but its distinctly visible in the browser.
Thanks for the reply...unfortunately it only works ok for labels and textfields, as soon as images and buttons are involved, the grouping and layout has a mind of its own. ie, i can no longer layour the images and button in flowlayout, everything just defaults to grid and stack on top of each other. I've tried every possible combination of transparent containers and groups and layout style but nothing works with the desirable result.