urlsnail/app/Models/BookmarkTag.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Relations\HasOne;
use Illuminate\Database\Eloquent\Relations\Pivot;

class BookmarkTag extends Pivot
{
    use HasFactory;

    public function parent()
    {
        return $this->belongsTo(Bookmark::class, 'bookmark_id');
    }

    public function tag(): HasOne
    {
        return $this->hasOne(Tag::class, 'id', 'tag_id');
    }
}