The function "shell()" does the trick.
WRT build window: Normally when running stuff from Slickedit, the "Build (.process)" buffer is not visible in the "Files" tool, and doesn't show up as an editor window.
For whatever reason, concur_command() does the equivalent of toggle_process_tab_output, and the shell() command does not.
BTW, "Send Output to Editor Window" appears to always be checked in the context menu of the Build tool.