To answer question 2b - creating another link to the script, it's certainly possible, but there is a slight complication and it does mean editing the script...
Here's the part of a script that registers it in the menus
(script-fu-register "script-fu-my-thing"
"<Image>/Filters/My Thing Menu Entry"
"My Thing"
"This thing does something"
"GimpChat"
"GimpChat"
"2001/04/12"
"RGB*, GRAY*"
SF-IMAGE "Input Image" 0
SF-DRAWABLE "Input Drawable" 0
SF-STRING "Text String" "DSR"
)
The important line here is: "<Image>/Filters/My Thing Menu Entry" which puts the script into the Filters menu with a label of "My Thing". This is the old way of doing things and won't allow you to create a second link to the script. It would have to be changed to this:
(script-fu-register "script-fu-my-thing"
"My Thing Menu Entry"
"My Thing"
"This thing does something"
"GimpChat"
"GimpChat"
"2001/04/12"
"RGB*, GRAY*"
SF-IMAGE "Input Image" 0
SF-DRAWABLE "Input Drawable" 0
SF-STRING "Text String" "DSR"
)
(script-fu-menu-register "script-fu-my-thing" "<Image>/Filters")
Where the register block now only specifies the menu label and the script-fu-menu-register specifies where in the menus it gets put.
From there it's simply a matter of adding a second or third.... menu-register block:
(script-fu-register "script-fu-my-thing"
"My Thing Menu Entry"
"My Thing"
"This thing does something"
"GimpChat"
"GimpChat"
"2001/04/12"
"RGB*, GRAY*"
SF-IMAGE "Input Image" 0
SF-DRAWABLE "Input Drawable" 0
SF-STRING "Text String" "DSR"
)
(script-fu-menu-register "script-fu-my-thing" "<Image>/Filters")
(script-fu-menu-register "script-fu-my-thing" "<Image>/contributed")
Which will appear in both the Filters menu and a "contributed" menu.
As Rod points out, doing the search backwards - i.e. knowing the menu entry but wanting to know the actual script file is helped by the script author putting the file name in the help text, but otherwise you would need to search the contents of the files using whatever tools you have on your system - GIMP can't do it for you.
Kevin