Is your feature request related to a problem? Please describe.
This surfaced in the nav design for Serverless. As the solution group will be the main and only group (other than the footer), we desire to not have it appear as collapsible.

Describe the solution you'd like
A group heading, in the EuiCollapsibleNavBeta, that is neither clickable nor collapsible. End result looking like:

Describe alternatives you've considered
We considered existing props to force it open, but accessibility concerns surfaced.

Desired timeline
This is for Serverless so mid-October (the 15th, ideally) availability in Kibana.

Additional context
The quote below is pulled from See this thread:

Can you rethink this ask? If it's truly crucial, the component used essentially can't be an accordion. Hiding the arrow is fine for visual users but there's still a ton of accessibility implications of accordions that's going to confuse screen reader users if we leave it in.

If we need a way to render a header with items that's not collapsible, that's fine, but I need to render it a different way than using an underlying EuiAccordion.