Heya Kanogwan,
The simple answer is no.
However! Depending on what you need, there are two ways to produce similar effects though.
-
Inherit from an existing widget - this is good if you want to add before/after html, or expand the available widget properties. Here's a good example in the Kentico docs that expands the default Kentico Form widget to have a heading
-
You can have a 1-level nested effect here by utilizing Page Builder Sections. You can create a section that only allows your inner widgets to be added inside it, and you can add properties to the section to modify its html in a similar fashion to a widget would - essentially creating a nested-widget approach. Here's Kenticos docs on developing Page Builder sections & here's a link to how you can start restricting what widgets can go inside a editable area (which can also be done for sections)