modeless
/ˈməʊdləs/adjective
1In mystical use: not manifested in a particular form; formless. Now rare.
2 Computing. Designating a program, system, or user interface that allows the user to perform various different types of action without having to switch between different modes of operation; specifically designating a dialog box that does not need to be responded to before the system will permit any other interaction.
Origin
Late 16th century (in an earlier sense). From mode + -less.