Dear Sir,
I checked attached odt file, I think i understood the point of adding a button to calculate discount based on lines. to disable auto calculation of total discount.
I'm working on odoo since 2009, it was version 4.2, I have had worked on each and every release of odoo then after, as of now actively working on odoo 11.
my journey of odoo was started right from odoo's own office in India, I worked there for 2 years, then after worked for odoo partners, acted as lead developer, also managed projects on site from requirements gathering to support and training.
I do have command on python, JavaScript, jQuery, css, qweb, sql etc, (i do code sometimes in PHP for integration projects), with several years of experience having a deep understanding of odoo framework and modules. i can make patches, bug fixes in odoo's core and also in core modules if needed.
Regards
Zahir