It's not always convenient or necessary to have a separate local installation of MODX. But there are some things that can be done on a local installation that are awkward at best to do on a remote installation. There is a way to have the best of both worlds.
zackw asked in a Slack conversation...
How can I work on a project good and fast as if locally, but changed files are almost immediately saved to the remote server? And my IDE can index the project and use all the fun tooling I need.
several people said...
"You can map a network drive to ftp" and variations.
One way is to use an SSH connection: Mount a remote filesystem using SSHFS
What's the Story?
Using SSHFS, you can mount a remote file system on your local system, then access it exactly as if it were a local system. The only difference will be that it's a little slower, since it's actually dealing with the remote files.
In Linux or OS X, this mounts the remote file system as any other file system is mounted to a specified directory. In Windows, it creates a new drive, just as if you added a new drive partition.
Alternatively, it appears that some IDEs have the ability to work with a remote file system as if it were local for project management. One example is NuSphere's PhpEd, another is JetBrain's phpStorm.