Combining my "fixup" button solution with Saq's idea about getting the links directly from the $:/Import tiddler, gives the following:
<$button> set missing created/modified fields <$list filter="[[$:/Import]links[]!has[created]]"> <$action-setfield created=<<now "YYYY0MM0DD0hh0mm0ss0XXX">> modified=< <now "YYYY0MM0DD0hh0mm0ss0XXX">> /> </$list> </$button> -e -- You received this message because you are subscribed to the Google Groups "TiddlyWiki" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/tiddlywiki/39cffd75-37a7-436a-b3cc-852823b6c509o%40googlegroups.com.

