Unable to differentiate between timeout and click on toaster notifications in Carbon Components for Svelte

I'm building an app using Svelte and Carbon Components (for Svelte). I'm trying to build an error notifications component which runs off an error store: When an error is thrown, a ToastNotification component is displayed across the top of the page; At the same time, there's a side panel (which the user can show/hide) which also lists all the unacknowledged errors.

Both the notifications across the top and in the side panel are obtained from the same store.

This image shows the toaster notification across the top of the page, along with its close icon.

This image shows the same error, but this time in the unacknowledged errors side panel.

What I want to do: If the user clicks x in the corner of the toaster notification then the error is considered acknowledged and is removed from the store. However, if the toaster notification displayed across the top of the page times-out, it will be hidden, but the same error should remain visible in the side panel (until the user clicks x on that toaster notification).

However, I can't find any way to distinguish between the toaster notification being hidden due to timing-out, and being hidden because the user has clicked x.

If I capture the on:close event I see the same custom event for both actions:

CustomEvent {isTrusted: false, detail: {…}, type: 'close', target: null, currentTarget: null, …}    isTrusted: false  bubbles: false  cancelBubble: false  cancelable: true  composed: false  currentTarget: null  defaultPrevented: false  detail:    timeout: true    [[Prototype]]: Object  eventPhase: 0  returnValue: true  srcElement: null  target: null  timeStamp: 12333  type: "close"  [[Prototype]]: CustomEvent

So it looks as if clicking x actually invokes a timeout, and consequently I can't see any way to differentiate between an actual timeout and the user clicking x.

Is there a way to differentiate between those two events?