Webextensions is not provide direct access from filesystem.
And this is only one loading logic:
Left click: reload from site
Right click: submenu for alternate one time loading methods (or for removing)
On this moment saving structure:
{bookmarkid: dialimage}.
Maybe in future I extend this to:
{bookmarkid: {dialimage: dialimage, dialimageorigin: fromurl}} but it changed only "reload all dials in dialgroup" logic.
But it is probably in future, because it is very rare pattern for me (I created this ext after dead of Speed Dial by Josep del Rio basically for yourself because some different Dials ([]) seems to me as malware).