Not aware of a way to put the new record row on the top. If the grid does not cover whole form, you could have a push button control to browse to the insert row (which is the special blank row at the end of the recordset). Otherwise, pick some other event and run LO Basic code to move cursor to the insert row. The overall structure will be something like the following (which is expanded here):
root_doc = ThisComponent
form_container = root_doc.Drawpage.Forms
main_form = form_container.getByName("MainForm")
main_form.last
main_form.moveToInsertRow()
Alternatively, you could use the UI to change over to add data only mode, although that could be confusing to user and I do not see a way to do it programmatically. The setting appears to be read only once the form is loaded.
(if this answers your question, pls accept the answer)
edit to add last command per comments