Have you seen
http://4js.com/online_documentation/fjs-fgl-manual-html/#fgl-topics/c_fgl_CodeEditing_005.htmlFor vim, syntax highlighting, code completion, goto definition, jump to tags.
I suspect the tags is dependent on using IMPORT FGL rather than linking.
I was first exposed to 4gl in the mid 90's (ie pre IMPORT FGL) and we had tags using vi then to navigate around our code. From memory the compilation process and/or a make option built up the tags file from our Makefile equivalents as this contained the information as to what 4gl were in an individual program