Add a Child Table Doctype in a anoter Child Table Doctype?

Hi @FHenry:

Yes. Seems that no many people showed interest at that time …
I am interested on this feature, I don’t how many people could be interested too.

I’ve made some experimental tentatives … but just for data output …

frappe.ui.form.on("YourChildDoctype", {
	form_render(frm, cdt, cdn) {
        var d = locals[cdt][cdn]
                        
        let html = `
    
        
        <style>
            /* Custom styles for the table */
            .wide-table {
                width: 100%; /* Make table wider */
            }
            .first-column {
                width: 60%; /* First column gets 60% width */
            }
            .text-right {
                text-align: right; /* Align text to the right for numeric columns */
            }
        </style>
    
    
    
    <div class="container mt-3">
      <table class="table table-bordered table-hover wide-table">
        <!-- Table Head -->
        <thead class="thead-light">
          <tr>
            <th scope="col" class="first-column">Description</th>
            <th scope="col" class="text-right">Qty</th>
            <th scope="col" class="text-right">Amount</th>
          </tr>
        </thead>
        <!-- Table Body -->
        <tbody>
          <tr>
            <td>Product 1</td>
            <td class="text-right">5</td>
            <td class="text-right">€50.00</td>
          </tr>
          <tr>
            <td>Service 2</td>
            <td class="text-right">2</td>
            <td class="text-right">€200.00</td>
          </tr>
          <tr>
            <td>Product 3</td>
            <td class="text-right">3</td>
            <td class="text-right">€150.00</td>
          </tr>
          <tr>
            <td>Service 4</td>
            <td class="text-right">1</td>
            <td class="text-right">€100.00</td>
          </tr>
          <tr>
            <td>Product 5</td>
            <td class="text-right">10</td>
            <td class="text-right">€500.00</td>
          </tr>
          <tr>
            <td>Service 6</td>
            <td class="text-right">4</td>
            <td class="text-right">€400.00</td>
          </tr>
        </tbody>
      </table>
    </div>
        
        `;

        frm.cur_grid.grid_form.fields_dict.your_html_field.html(html);
	}
});

Just a try, without fetching data from other doctypes, but is doable.
Hope this helps.