Need custom value under subject field when agent click on forward button in incident

Summary

Need custom value under subject field when agent click on forward button in incident

Content

Hello Service Cloud Specialist,

Need custom value under the subject field when the agent clicks on the forward button in the incident?

Example: When the agent clicks on the forward button in the incident then a dialog box gets appear with the following details "To, CC, BCC, and Subject value. I want the standard subject value should change to a custom value.

Please refer to the attached screenshot for your reference. 

Regards,

Vikash

Vikash