No, You can only use nested widgets with HTML Templates. This is a limitation of WP shortcodes. Reference : https://pastebin.com/Axxs0TzK
In short, the inner one needs to be embedded in html.
[wptabs]
[wptabtitle]1st tab[/wptabtitle]
[wptabcontent] Some content inside the tab + an accordion....
<!-- Same structure as the tabs, except for the class name .wp-accordion -->
<div class="wp-accordion wpui-light">
<!-- nested tab first -->
<h3 class="wp-tab-title">Tab 1</h3>
<!-- First tab's contents -->
<div class="wp-tab-content">
All the contents of first tab goes here....
</div><!-- end first tab -->
<!-- Like so, Second panel -->
<h3 class="wp-tab-title">Tab 2</h3>
<div class="wp-tab-content">
Contents of the second tab
</div>
</div><!-- end class wp-accordion -->
.... Other content below acccordion.
[/wptabcontent]
[wptabtitle]2nd tab[/wptabtitle]
[wptabcontent] Some content inside the tab.... [/wptabcontent]
[/wptabs]
