Currently, user-defined variables can only be renamed in the variable manager if they are not referenced in the project. Variables that are already in use cannot be renamed, which limits flexibility.

Suggested improvement:
Allow renaming of user-defined variables directly in the variable manager, with all references in the project being updated automatically.

Benefit:
- Improves maintainability and readability of projects.
- Ensures consistent naming conventions even after a variable is already in use.
- Avoids workarounds like creating duplicate variables with corrected names.