If you’re tired of uploading WP-Config.php after each change you make, consider using a brand new plugin by Dgwyer called Config Constants. It currently has support for nine commonly used constants with more possibly being added in the future. While the plugin does not actively add constants to WP-Config.php, it provides a way for you to enable/disable the ones that are discovered. The options for the plugin are fairly straightforward as you can see via the following screenshot:
One of the coolest features of this plugin is the information icon next to each constant which is linked directly to its corresponding Codex page. One other nice feature is the ability for two-way editing:
Also, a key feature of the Plugin is the support for two-way editing. This means you can still edit wp-config.php constants manually if you wish and your changes will be automatically synchronized with Plugin settings. Likewise, if you update the value of a constant via the Plugin options page then wp-config.php is immediately updated.
While I’m not sure how many power users are going to bypass their usual method of changing/uploading the WP-Config file to installing this plugin to perform the changes, at least the plugin exists for those that prefer to go this way. Just remember to backup the original WP-Config file, just in case. If you would like to give Dgwyer direct feedback concerning this plugin, you can do so in the comments or via the following forum thread.