This Python script can be used to replace shapes in a SWF file with ones you have drawn in Inkscape and saved as SVG. It is a cheapskate alternative to a full flash authoring environment, if all you want to do is tweak somebody else's flash mod.
You will need to download and install a separate tool named swfmill before this script can run, as well as a Python interpreter (version 3). There are no other dependencies. It's normal usage is:
$ python3 sdtmill.py origmod.swfml myshapes.svg mymod.swf
Which takes the vector layers defined in myshapes.svg, and replaces the shapes in origmod.swfml which have identical names to the layers. The output is written into mymod.swf and not into any other file.
There's a lot more to it than that. Read the documentation within the script. You can get command-line help from the script itself with its --help option:
$ python3 sdtmill.py --help
Almost everything you need to know is documented there. Alternatively you can open the script up in a text editor to see how it works.
Tested in Debian Linux.