MultilaunchWarning

MultilaunchWarning is a global option that specifies whether a warning is given when you try to modify user preferences while running two copies of the Wolfram System simultaneously.

Examples

Disable the multilaunch warning:

SetOptions[$FrontEnd, MultilaunchWarning -> False]

Check the current setting:

CurrentValue[$FrontEnd, MultilaunchWarning]

Please visit the official Wolfram Language Reference for more details.