Hi @daroot,
If here you are talking about the Creat New Request part, then within the OnSelect property of the Save button, the Email function is:
Office365.SendEmail(Office365Users.UserProfile(NewLeaveApproverID).Mail, "Leave Request Approval", emailHtml,{IsHtml:true, Importance:"normal"});

If additional Email need to be sent, then please consider add another line behind the formula above:
Office365.SendEmail(
Office365Users.UserProfile(NewLeaveApproverID).Mail,
"Leave Request Approval",
emailHtml,
{IsHtml:true, Importance:"normal"});
Office365.SendEmail(
SupervisorEmailAddress,
"Leave Request Approval",
emailHtml,
{IsHtml:true, Importance:"normal"});
Regards,
Michael