Support having an active segment group

[MichaelBuessemeyer]

Detailed Description

There is an inconsistency between the trees and segments tab: The trees tab can have an active group id which leads to visual highlighting and enabling adding new trees to that group, but the segments tab does not.

I'd say it would be nice to have an active group in the segments tab.

Context

No specific context

Potential features

• Highlighting an active segment group (e.g. via search or click)
• Add new selected segments as children to that group