To change a password in a scheduled task in Windows, define this template in a child credential, so after the parent credential is changed, the password in scheduled task will be changed too.
Create a new template, in the menu Executions > Settings > Templates :
Name: Windows Scheduled Task
Executor: Windows RM
Execution Type: Password change
Content:
powershell Set-ScheduledTask -TaskName “[ADD_INFO#]” -User “[username#]” -Password (ConvertTo-SecureString -String “[#NEW_PASSWORD#]” -AsPlainText -Force)