Editing plugins in WordPress:
Plugins are the editable files, among the many, used in WordPress. When you want to edit the codes of the plugins, you can do the same by going to the Plugin Editor Screen. This screen lets you modify the snippets and bring about the necessary changes. There are lots of things, this built in Plugin editor lets you to do.
How to choose the plugin to be edited?
With thousands of plugins and chances of you being installed, 1/10th of them, you need to first choose the plugin you need to edit. For this, you go to the drop down menu in the top right of the WordPress and select the plugin, you need to edit. The names of the plugins are listed here.
Under the selection menu, the plugin files that can be edited are listed. There are file links available and click on them. This lets you paste the text of the files in the textbox, enabling you to edit the plugin.
It becomes important to look up the documents, and this can be found under the editor. There is a list of the function names available in a plugin. Select a function and tap the Lookup button. The documentation can be seen in phpdoc.ordpress.org. You can also find the same in php.net.
Updating the Files:
Once you have made the changes, make sure, you have click the Update File button, to save the changes. A splash message that tells you that the file has been changed successfully appears, once you have clicked this button. If you can see no message, the changes are not saved, so repeat the process. When you cannot see the update file button, then the file is not writable.