So I found out, that the problem is caused only by blurring. Without blurring, the export goes quite well even with trasparency (but it's still VERY slow on 300 DPI).
The export goes unbelievably slowly with blur efffect on some objects. Rendering of a drawing with 4960x7016 resolution took already 5 hours and it's still half way to go :-/
Btw. is there any way to set DPI when creating a new document? A2 poster with resolution 1488x2104 is real nonsense
In the end I would like to thank developers for creating such amazing application.
![Wink ;)](images/smilies/icon_e_wink.gif)
When it will have panel docking and faster rendering, Adobe and Corel will go to hell
UPDATE: After 8 hours of labor, image is finally exported...but broken. 3 blurred transparent objects weer ignored, 4 were OK