To add additional restriction to the poReceiptLinesSelection data view, you should invoke Select method on base view and inspect each item in returned PXResultSet independently to decide if it complies with additional restriction(s):

public class APInvoiceEntryExt : PXGraphExtension<APInvoiceEntry>
{
    [PXCopyPasteHiddenView]
    public PXSelect<APInvoiceEntry.POReceiptLineAdd> poReceiptLinesSelection;

    public virtual IEnumerable POReceiptLinesSelection()
    {
        foreach (var record in Base.poReceiptLinesSelection.Select())
        {
            // Additional restriction goes here
            if (true == true)
            {
                yield return record;
            }
        }
    }
}

This approach perfectly works with the poReceiptLinesSelection data view, due to lack of paging and aggregation in the implementation of base view. To compose result set, poReceiptLinesSelection view requests necessary data from database and performs all calculations on the application side.

public class APInvoiceEntry : APDataEntryGraph<APInvoiceEntry, APInvoice>, PXImportAttribute.IPXPrepareItems
{
    ...

    [PXCopyPasteHiddenView]
    public PXSelect<POReceiptLineAdd> poReceiptLinesSelection;

    public virtual IEnumerable POReceiptLinesSelection()
    {
        APInvoice doc = this.Document.Current;
        if (doc == null || doc.VendorID == null || doc.VendorLocationID == null) yield break;
        if (doc.DocType != APDocType.Invoice && doc.DocType != APDocType.DebitAdj)
            yield break;

        string poReceiptType = (doc.DocType == APDocType.Invoice) ? POReceiptType.POReceipt : POReceiptType.POReturn;

        HashSet<APTran> usedRecceiptLine = new HashSet<APTran>(new POReceiptLineComparer());
        HashSet<APTran> unusedReceiptLine = new HashSet<APTran>(new POReceiptLineComparer());

        foreach (APTran aPTran in Transactions.Cache.Inserted)
        {
            if (aPTran.ReceiptNbr != null && aPTran.ReceiptType != null && aPTran.ReceiptLineNbr != null)
                usedRecceiptLine.Add(aPTran);
        }

        foreach (APTran aPTran in Transactions.Cache.Deleted)
        {
            if (aPTran.ReceiptNbr != null && aPTran.ReceiptType != null && aPTran.ReceiptLineNbr != null && Transactions.Cache.GetStatus(aPTran) != PXEntryStatus.InsertedDeleted)
                if (!usedRecceiptLine.Remove(aPTran))
                    unusedReceiptLine.Add(aPTran);
        }

        foreach (APTran aPTran in Transactions.Cache.Updated)
        {
            APTran originAPTran = new APTran();
            originAPTran.ReceiptNbr = (String)Transactions.Cache.GetValueOriginal<APTran.receiptNbr>(aPTran);
            originAPTran.ReceiptType = (String)Transactions.Cache.GetValueOriginal<APTran.receiptType>(aPTran);
            originAPTran.ReceiptLineNbr = (Int32?)Transactions.Cache.GetValueOriginal<APTran.receiptLineNbr>(aPTran);

            if (originAPTran.ReceiptNbr != null && originAPTran.ReceiptType != null && originAPTran.ReceiptLineNbr != null)
            {
                if (!usedRecceiptLine.Remove(originAPTran))
                    unusedReceiptLine.Add(originAPTran);
            }

            if (aPTran.ReceiptNbr != null && aPTran.ReceiptType != null && aPTran.ReceiptLineNbr != null)
            {
                if (!unusedReceiptLine.Remove(aPTran))
                    usedRecceiptLine.Add(aPTran);
            }
        }

        foreach (LinkLineReceipt item in PXSelect<LinkLineReceipt,
            Where<LinkLineReceipt.vendorID, Equal<Current<APInvoice.vendorID>>,
            And<LinkLineReceipt.vendorLocationID, Equal<Current<APInvoice.vendorLocationID>>,
            And<LinkLineReceipt.receiptCuryID, Equal<Current<APInvoice.curyID>>,
            And<LinkLineReceipt.receiptType, Equal<Required<POReceipt.receiptType>>,
            And<Where<LinkLineReceipt.orderNbr, Equal<Current<POReceiptFilter.orderNbr>>, Or<Current<POReceiptFilter.orderNbr>, IsNull>>>
            >>>>>.SelectMultiBound(this, new object[] { doc }, poReceiptType))
        {
            APTran aPTran = new APTran();
            aPTran.ReceiptType = item.ReceiptType;
            aPTran.ReceiptNbr = item.ReceiptNbr;
            aPTran.ReceiptLineNbr = item.ReceiptLineNbr;
            if (!usedRecceiptLine.Contains(aPTran))
                yield return (PXResult<POReceiptLineAdd, POReceipt>)ReceipLineAdd.Select(item.ReceiptNbr, item.ReceiptType, item.ReceiptLineNbr);
        }

        foreach (APTran item in unusedReceiptLine)
        {
            yield return (PXResult<POReceiptLineAdd, POReceipt>)ReceipLineAdd.Select(item.ReceiptNbr, item.ReceiptType, item.ReceiptLineNbr);
        }

    }

    ...
}