Currently I do this in a BAT file:
Inkscape.exe --file "some.svg" --export-png "some_64.png" --export-width 64
Inkscape.exe --file "some.svg" --export-png "some_96.png" --export-width 96
Inkscape.exe --file "some.svg" --export-png "some_128.png" --export-width 128
But that is kind of slow to run Inkscape 3 times in a row and open the same file, plus you have to save the source svg file prior to running the export BAT and make sure the BAT gets the right filename.
So I'm wondering is there a tool (export plugin) that allows to automate the export from inside the Inkscape, something like Export Bitmap dialog, but with scripting support?