No, there is no plugin. Up to now it's a more or less manual job as all programs do not offer an export for all metadata I like to see in calibre (and a lot of file formats do not offer metadata too. Taking this in mind, you need programs like Truesizer to generate the whole bunch of information (and most of them do not offer an export of all data).
Wilcom is the only program I know so fare that use a SQL based library with a combination of embroidery and design workflow software. But that is a expensive solution.
What I am doing with our files and calibre is from that perspective a lot cheaper but need for now (a lot) more manual work. Each embroidery file (in all formats) for a collection have an manually exported image as "cover" and a worksheet with design information. In addition there are project files and sometimes a set of additional files for a collection.
You need to spend a lot of time in generating, collecting, classifying and archiving these information as there are no existing general databases of metadata for commercial embroidery designs you can run a query. And believe me or not, if you talk about embroidery, everyone have a own understanding of "good embroidery metadata" and "classification ideas". Commercial embroidery companies and designer too.
Well, I too and it is a never ending "development" process over the time.
I build up my own small embroidery library within calibre as I hate stupid directory structures for library things.
Thanks to Kovid and all the supporter. calibre is a nice and flexible pice of software
... for the moment only a direct support for embroidery files is missing 