<TelerikGrid @ref="@GridRef"
            OnEdit="@OnGridEdit" />

@code {
    private TelerikGrid<Product> GridRef { get; set; }

    private bool ShouldCancelLastRowEdit { get; set; }

    private bool ShouldEditFirstCell { get; set; }

    private async Task AppendGridRow(string editField)
    {
        // ...

        if (lastKey == "Enter" && editField != nameof(Product.Name))
        {
            ShouldCancelLastRowEdit = true;
        }
    }

    private async Task OnGridEdit(GridCommandEventArgs args)
    {
        if (ShouldCancelLastRowEdit)
        {
            ShouldCancelLastRowEdit = false;

            args.IsCancelled = true;

            ShouldEditFirstCell = true;
        }
    }

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        if (firstRender)
        {
            // ...
        }

        if (ShouldEditFirstCell)
        {
            ShouldEditFirstCell = false;

            var state = GridRef.GetState();

            Product lastItem = state.OriginalEditItem = GridData.LastOrDefault();
            state.EditField = nameof(Product.Name);
            state.EditItem = new Product() { Id = lastItem.Id }; // cloning may be more appropriate

            await GridRef.SetState(state);
        }

        await base.OnAfterRenderAsync(firstRender);
    }
}