How to setup remote debugging on Weblogic clustered environment?

I figured it out!

When you start the cluster nodes through WebLogic console page, The node manager handles the start-up of each node in some way, so it does not run each node's [startWebLogic.cmd] file!

I found that you can set remote debugging arguments for each node through the console page itself, so that the node manager will pass those parameters to each node when it attempts to start it.

Below is how I did that (Edit: on WebLogic 12c):

1. Open WebLogic console page (e.g: localhost:7001/console)
2. On the left side of the page, go to Environment > Clusters
3. Find the name of your cluster environment and click on it
4. In the "Configuration" tab, open the "Servers" sub-tab
5. At the bottom of the page, you'll find a table of all the cluster nodes you have.
6. Click on one of the nodes (servers).
7. In the "Configuration" tab, open the "Server Start" sub-tab
8. Scroll down a bit and you'll find a Text Area named "Arguments", fill it with the remote debugging arguments: -Xdebug -Xnoagent -Xrunjdwp:transport=dt_socket,address=4000,server=y,suspend=n
9. Click "Save", and repeat steps 6-8 on all the other cluster nodes.

And you are done!