Welcome to the forums!
Maybe you are looking for something like this:
Halts the macro and displays string in a dialog box. The macro proceeds when the user clicks “OK”. Unlike showMessage, the dialog box is not modal, so the user can, for example, create a selection or adjust the threshold while the dialog is open. To display a multi-line message, add newline characters ("\n") to string. This function is based on Michael Schmid’s Wait_For_User plugin. Example: WaitForUserDemo.
Using this function you can halt the macro at a particular point, define a new line selection and then press “OK” to continue.