suite/project_acceptance/views/project_portal_templates.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>

    <template id="portal_my_task_inherit" inherit_id="project.portal_my_task">
        <xpath expr="//div[@class='mt32']" position="before">
            <div class="row justify-content-center text-center d-print-none pt-1 pb-4">
                <div t-if="not sale_order_exceptions" class="col-sm-auto mt8">
                    <!-- <a role="button" class="btn btn-primary" data-toggle="modal" data-target="#modalaccept" href="#"><i class="fa fa-check"/>Accept</a> -->
                    <!-- <a role="button" class="btn btn-primary" t-attf-href="#" style="color: #ffffff"><i class="fa fa-check"/> Accepted</a> -->
                    <a role="button" class="btn btn-primary" data-toggle="modal" data-target="#modalaccept" href="#" style="color: #ffffff"><i class="fa fa-check"/> Accepted</a>
                </div>            
                <div class="col-sm-auto mt8">
                    <!-- <a role="button" class="btn btn-danger" data-toggle="modal" data-target="#modaldecline" href="#"> <i class="fa fa-times"/>Decline</a> -->
                    <a role="button" class="btn btn-danger" t-attf-href="#" style="color: #ffffff"> <i class="fa fa-stop-circle"/> Declined</a>
                </div>
                <div class="col-sm-auto mt8">
                    <!-- <a role="button" class="btn btn-secondary" href="#discussion"><i class="fa fa-comment"/> Feedback</a> -->
                    <a role="button" class="btn btn-warning" t-attf-href="#discussion" style="color: #ffffff"><i class="fa fa-comment"/> Feedback</a>
                </div>
            </div>
        </xpath>
    </template>

</odoo>