[Vuejs]-Vuetify v-data-table within v-data-table: content in extended-item slot malfunction

You can do it changing :items="tabItems" by :items="[item]" (i put inside array because one item alone is not legible by :items v-data-table.

If you call tabItems you will iterate over all items again so its better to use filtered expanded-item item instead do hard work manually.

I tried in your sandbox, you can change line 54 with my suggestion and you could check that its working well.