Solved
make "offset line" to be editable
Q5:How to convert the "offset of line_A" into a common or normal curve like an editable freehand curve?
In Creo when offsetting an entity, you are creating a child of the references selected for offset. You have defined a parent child relation in the model and by design the new entity is dependent on its parents and cannot be modified directly.
If you are trying to implement some design intent that prompts your question, then describe the use case and someone may respond with a solution.
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