Requirement: Implement a multi-level bookmarking feature.

Details: The goal is to have multiple modules in the code logic, with clear hierarchical levels. If there are only one or two levels without the capability for nesting, it's challenging to visually discern the relationships between different levels and modules. Additionally, currently a single line of code can only be associated with one bookmark. This limitation prevents a line of code from being included in multiple bookmark groups, reducing the flexibility and usability of the bookmarking system.