Encrypted cerficiate signature for server certificate and intermediate certificate in packet capture
The intermediate certificate is signed by its issuer(a root CA or another intermediate CA), using the private key of the issuer's certificate.

The server certificate is signed by the intermediate CA at the lowest level of the certificate chain.


  when configuring the certificate chaining in the server, the imported intermediate CA already has the certificate signature encrypted?


Yes, when you want a certificate for your domain, you ask for it from an intermediate CA. After the CA verifies that you're the actual owner of the domain, they give you a certificate signed by the CA's private key. Then you can configure to use it on your server.

The intermediate certificates are simply available to the public, they are sent by the server generally for clients that don't have them installed.