If it is a work produced by professional conduct, you do not have the copyright, but you have the right of signature. However, your right of authorship is affected by many factors:

The degree of independent completion of your work. For example, if the director tells you how to design, even if you complete 99.9% of it, the signing rights belong to the director to a large extent. Because design is divided into many links, 99.9% of what you are responsible for has no technical content.

Do you have the ability to sign independently and make the drawings effective? In some engineering designs, a qualified designer's signature is required to make the drawings effective. If you do not have officially certified qualifications, signing will only invalidate the drawings.

Whether the drawing meets the conditions for multiple signatures. Some works have limited spots for signatures, and generally only the main creators will be signed. The name of the draftsman will not be signed.

Even if official qualifications are not required, can your reputation make customers feel that it is an acceptable treatment? Because some customers are looking for a company to design, and they may be looking for some leaders. Forwarding you a signature design may ruin the business. Generally speaking, if you are someone's subordinate and use the name of the director, the client will feel that you are valued.

I think there is no need to worry about this issue. It is your own ability to learn. Engineering drawings and signatures are subject to legal liability. What are you doing to argue about this?