You should use the Webview widget from the NativeMobileResources module.
HTML/JS snippet is not supported in native.
Try downloading the the mpk file for the widget from GitHub repo https://github.com/mendix/HTMLSnippet/tree/master/dist
Place this mpk file in your project directory → widgets folder. If there is existing file, replace it. Restart Studio pro, open your project and see if you can place that widget in any form.