If you add the username to the scp command, IOS-XE only cares about the destination filename and password, so something like this should work:
- name: Execute SCP copy command
ansible.netcommon.cli_command:
command: >-
copy scp://{{ source_username }}@{{ remote_host }}/{{ new_file }} flash:/{{ new_file }} vrf Mgmt-vrf
prompt:
- "Destination filename"
- "Password"
answer:
- "{{ new_file }}"
- "{{ srv_net_password }}"
check_all: true
no_log: true # So password is not exposed.
vars:
ansible_command_timeout: 3600
ansible_connect_timeout: 3600