How to focus on tabs when the sidetabs viewtemplate is revealed to navigate through tabs using Tab key

I have a custom viewtemplate to float what I call as sidetabs to the right of the tiddler body using reveal widget. In the sidetabs, I am showing some tiddlers related to the currentTiddler using the horizontal tab macro. See the template used here.
Here is an example of how it looks.

I have a keyboard shortcut Alt+A to reveal this sidetabs. Once the sidetabs is open I want to navigate through the tabs using Tab key. But I think the focus is on the tiddler title or viewtoolbar buttons when the sidetabs is open. So I have to press the Tab key many times to bring the focus on the tabs within the sidetabs. How to get the tabs in the sidetabs focused when the sidetabs is opened.