Hi Nikos,
Add below code in the CSS/Custom Stylesheet section of the portal and click Save & Publish. After a refresh of the customer portal, the field name and field should be hidden. Because there are made hidden, the checkbox to request for someone else still shows on the same position.
body[page="catalog_item"] #side-modal #side-modal-content .place-request-container .control-label label
{
visibility: hidden !important;
}
body[page="catalog_item"] #side-modal #side-modal-content .place-request-container .control-element input {
visibility: hidden !important;
}
Let me know if this works for you.
Regards,
Rutger Bockholts
Freshworks