:quit-when-no-windows keyword argument to deliver.
set-quit-when-no-windows can be used at run time in a delivered application to override the value of the
:quit-when-no-windows keyword to deliver. This can be useful if the application runs in various modes, some with windows and some without. It has no effect in a non-delivered application.
If on is
:check, then the application will quit immediately if there are no open windows at the current time. Unlike with
:quit-when-no-windows t, this occurs even if the application has not opened any CAPI windows so far. If there are open windows currently, then it turns on quitting like when on is
LispWorks User Guide and Reference Manual - 20 Sep 2017