"EnterSubsession"

"EnterSubsession" is a front end token that starts an interactive session in the specified kernel during an evaluation.

This token is equivalent to the menu command Kernel Evaluation Enter Subsession.

This token requires a parameter, which can be the name of the kernel or Automatic if you want the default kernel. See Dialog or The Mathematica Book: Section 2.14.2 for more information.

To execute a front end token, you typically evaluate a command of the form FrontEndExecute[FrontEndToken[token]].