Operating system: FreeBSD 13.0
Note: 
 In code excerpts and examples, the long lines are folded and then indented to make sure they fit the page.
Install Graphviz Visual Editor
App: 
 Graphviz Visual Editor 
 About
 “A web application for interactive visual editing of Graphviz graphs described in the DOT language.”
 http://magjac.com/graphviz-visual-editor 
 (Retrieved on Feb 8, 2022)
% sudo vm list
NAME       DATASTORE  LOADER  CPU  MEMORY  VNC  AUTOSTART  STATE
debianvm1  default    grub    1    512M    -    No         Stopped
% sudo vm start -f debianvm1
Log in to Debian GNU/Linux VM.
Debian GNU/Linux 11 debianvm1 ttyS0
debianvm1 login: 
Install Git and npm.
$ sudo apt install git
$ sudo apt install npm
$ mkdir ~/scratch
$ cd ~/scratch
$ git clone https://github.com/magjac/graphviz-visual-editor
$ cd graphviz-visual-editor/
$ npm install
$ make
$ npm run start
---- snip ----
Compiled successfully!
You can now view graphviz-visual-editor in the browser.
  Local:            http://localhost:3000/
  On Your Network:  http://192.168.8.19:3000/
Note that the development build is not optimized.
To create a production build, use npm run build.
Use a Web browser - on either GNU/Linux Debian guest VM or FreeBSD host and open http://192.168.8.19:3000/.
To run it again:
$ cd ~/scratch/graphviz-visual-editor
$ npm run start