multi

enables/disables mode when several panels can be visible at once

boolean|string multi;

true

all panels can be expanded as well as collapsed at a time;

false

only one panel can be (and must be) visible at a time;

"mixed"

all panels can be expanded at a time, but you cannot close them all. One pane remains visible.

webix.ui({
    cols:[{ view:"accordion",
        multi:true,
        ...
    }]
})