__layout.svelte

<script>
    import ModalList from "@mavthedev/svodals";
    import AModal from "$lib/AModal.svelte"
    const modals = [
        {
            id: 'data',
            component: AModal
        }
    ]
</script>

<ModalList modals={modals}>
    <slot />
</ModalList>

$lib/AModal

<script>
    // Whatever data you require
    export let data;
    //  Function close(data) => callback(data)
    export let close;
</script>

{data.info}
<button on:click={() => close(true)}>
    OK
</button>
<buttton on:click={() => close(false)}>
    No
</button>

index.svelte (or any other route)

<script>
    import { getModalContext } from "@mavthdev/svodals";

    const modalAPI = getModalContext()

    function create() {
        //                  ID      Callback    Data passed to modal
        modalAPI.addModal("data", console.log, {
            info: "Save Data?"
        })
    }
</script>

<button on:click={create}>
    Create Modal
</button>