Add "Add attachment link" for Quotation

1. We found all sales document create, update, view are using
        a. \sales\sales_order_entry.php
        b. Each type have a menu session
    2. Found the applied menu link at invoice session
    3. submenu_option(_("Add an Attachment"), "/admin/attachments.php?filterType=".ST_SALESINVOICE."&trans_no=$invoice");
    4. That is the menu link with type of document and reference no.
    5. We just copy this link to right menu session
    6. And change the document type and reference variable
    7. ST_SALESORDER = sales order, ST_SALESQUOTE = Sales quotation, ST_CUSTDELIVERY = Sales delivery

Then all sales have the link to add attachment after create or update, like direct invoice

I think what you're looking for is this: https://ibb.co/NYBnHkw

in sales_order_view.php add a new function:

function attach_link($row) 
{
    global $trans_type;
        return pager_link( _("Attach Documents"),
            "/admin/attachments.php?filterType=".$trans_type."&trans_no=" .$row['order_no'], ICON_ATTACH);
}

then under-> elseif ($trans_type == ST_SALESQUOTE) {
add ->  array('insert'=>true, 'fun'=>'attach_link')

*you'll have to create/define ICON_ATTACH in includes/types.php