Add option to expand specific term tree levels by default

Problem/Motivation

Currently, the taxonomy term tree widget forces an "all or nothing" approach to expanding term tree levels.

In complex or deep taxonomy structures (e.g., e-commerce categories or large organizational charts), content editors and site administrators often need level 1-x terms to be visible immediately upon page load to streamline their workflow. Forcing users to manually click and expand multiple nested levels every single time they interact with the tree is inefficient and degrades the user experience.

There is currently no configuration option to specify which exact levels of a term tree should be expanded by default.

Steps to reproduce

Proposed resolution

Add option to expand specific term tree levels by default.

Remaining tasks

User interface changes

API changes

Data model changes