I see this is a bit of an old query, but just in case:

Currently, the ability to have the submenu open by default is not a native option in Elementor. This should be achievable with custom code. You can get assistance for custom code on our GitHub, which our developers monitor – https://github.com/elementor/elementor.

In addition, you’re welcome to open a feature request on our Github, as well (Ref: https://github.com/elementor/elementor/blob/master/.github/CONTRIBUTING.md).

Kind Regards,