Is it possible to access the node-red dashboard externally from another network without using the cloud?
Yes. Search the forum. Asked and answered many times (hint: this is not a simple subject)
What do you mean by that? Across the internet? or a cloud solutions provider? or just across a private LAN?
It probably depends what you mean by using the cloud.
Is this for industrial or personal use?
If your network has a static IP then, firewalls permitting, you can connect from the internet.
A ddns service would work too, but that's in the cloud?
You could set up a VPN.
Actually, I want to access node-red dashboard on external network, without needing to be on server network.
You could run node-red on the external network, with it's own dashboard and send the values for display using mqtt.
Which would probably involve a cloud based broker, but it would isolate the dashboard from your main node-red server.