It is possible to clone Custom Fields with Deep Clone for Jira. If some Custom Fields weren’t cloned, you can try the following solution.
The custom field must be configured in both projects.
The name of the custom field must match in both projects, if you clone between company-managed (classic) and team-managed (next-gen) projects.
Some Jira Service Management fields and other custom field types cannot be cloned.
"Date of First Response"
"Username of last updater or commenter"
"Domain of Assignee"
"Domain of Reporter"
"Number of attachments"
"Number of comments"
"Last public comment date"
"Last commented by a User Flag"
"Participants of an issue"
"Days since last comment" Automatically set by Jira
"Rank" Cannot be cloned. You can use the "Rank cloned issues" function after a Bulk Clone instead.
JSM "Request Type Not supported by JSM. Get in touch with us, if you need to clone that field.
JSM "SLAs" Automatically set by JSM
JSM "Approvals" Not supported by JSM. Get in touch with us, if you need to clone that field.
JSM "Satisfaction" and "Satisfaction date" Can only be set by JSM
JSM "Request language" Can only be set by JSM