www.iforce2d.net

Cool. Just two comments to script code:
1 In layout.json have "desc": "move along edeg" instead edge. Just typo
2 In four places have local coord (.pos) in code, but script only work correctly for me when I changed this to the world pos (.wpos).

Thank You Chris, I'm glad.
Here the next version. It's already can handle the selected bodies too.

I'm wrote a little script, which align all selected vertices to the grid.
Maybe will be useful, here is it.

I totally understand and accepted your answers.

ps
Just in case maybe better solution if have standalone IMPORT for the Json in file menu, isn't it ?
And R.U.B.E is fantastic, congratulation

If you set up the custom properties again (in the Scene settings dialog) then the values will show up again.

Yeah, I noticed. But this solution would be very inconvenient, and once the information is there, so why not show it?

If scene export to json-format, the saved file contains the defined customproperties.
But when load back file to the editor, all customproperties missing.
( The rube-format save-load ok )