There is no separate placeholder for this field in the schema. Including it in a schema will be examined in the next round of revision.
However, as a workaround, the field of “Other Charges (Invoice Level)” can be used to mention TCS where it doesn’t form part of taxable value.
May further note that the INV-01 schema only reports specified invoice particulars to IRP. Once IRN is obtained from the portal, the business may add any other elements not relevant to GST while finally issuing an invoice to the buyer.