As far as I can see, the event border seems to work fine on all-day events:
onBeforeEventRender: args => {
args.data.borderColor = "red";
}
If it doesn’t show properly in your app, I recommend inspecting the element and its styles using browser developer tools. This lets you see if the border color is applied and if there is a rule that overrides it.
Unfortunately, the scrollbar for the all-day event section is not available at the moment.