Hi all.

Is it possible to set Document's Metadata or properties like size (maybe even own formats) which will be used by default each time Inkscpae is started?

It can be really annoying to set the same Creator info or not having the date prefilled to file's creation. It is also easy to forget about such details.
Similar thing is that the amount of document's formats is limited and previously selected size is not remembered.

Is there any "trick" to make it work better or is it on "ToDo" list?

Setup the document the way you want it, then save it in the "templates" folder. Alternatively, you could edit the "default.svg" file in the "templates" folder, but I'd recommend you just save a new file. Then, when you select File > New from the menu, you'll see your new template file in the list that pops up.

See the following links for info on where/what the templates folder is.
http://tavmjong.free.fr/INKSCAPE/MANUAL ... -Open.html
http://tavmjong.free.fr/INKSCAPE/MANUAL ... -Templates