Hi,

You can inherit the sale order line view and add a button inside the line similar to the Register Lots, Packs and Location button in picking.
Add the button after your custom fields on sale.order.line view inside your XML file.
.xml

<button name="button_function" string="String you want" type="object" icon="fa-icon_you_like"
                                            width="0.1"
                                            options='{"warn": true}'/>

.py

class SaleOrderLine(models.Model):
_inherit = 'sale.order.line'

 def button_function(self):
"""And then write your function"""

Regards