How to get issue id in Calculated Custom Field?

[Puján Z]

I am using a Claculated Custom Field to create a link for adding sub-tasks. This comes on the view screen to make it easier for users to add a sub-task. The link consists of issue id (and not issue key). I can create a link with issuekey, but I don't know how to access issue id (with issue.get("")). I tried id, issueId and issueid, but none seem to work.

Any help is appreciated :)