[rozyczko]

Model Linking Functionality:

• Added planModelLink, linkModels, and removeLinkedParameter methods to both the backend (sample.py) and frontend QML files, enabling users to preview, apply, and remove model links, including selective parameter tying.
• Updated the backend to track linked parameters, represent each model link as a single constraint row, and allow removal of entire links or individual tied parameters.

GUI Enhancements:

• Integrated new functions into the frontend for planning and applying model links, and for removing linked parameters via the GUI.
• Updated the constraints sidebar to display model links distinctly, including their tied parameters and support for removal actions.

Other Improvements:

• Improved placeholder text for constraint expressions to better match typical usage.