No it's not possible and yes we've all been asking for this for ages.   For some reason it's not at the top of the EasyEDA developers list even though it's the most obvious missing feature in the whole product. Maybe the developers don't have two monitors and don't realise that most people do nowadays :-)

The only solution i found until now is to open the online edito in one monitor and the desktop on in another

You can run more than one instance of the online version in different tabs of the browser so you can also move the browser tabs into separate windows. IIRC, the problem however, is that the synchronisation during Update PCB.../Import Changes... and with Cross Probing probably does not work.

@andyfierman It doesn't sync at all.   And both myself and the OP use the Desktop version as the browser one is so clunky.

@MikeDB Speaking as a developer, all developers that I know use multiple monitors :)

@magronlundjr Yes - I have three in front of me now :-)   And another two behind me testing the latest PCBs I meant the software developers.  We in the West tend to use several but I've noticed this isn't always the case in Asia.

@MikeDB I meant software developers as well :/

ALL EasyEDA coders are using tow monitors, just as @MikeDB told. There are too many others key features need to be  provided.   EasyEDA is almost  ten years old,  we are thinking about a new bit version, maybe named as EasyEDA pro, in that version, will support tow monitors, the key point, EasyEDA can be used in complex PCB design, maybe can work smooth enough in  big PCB( more than 20K pads , 5K components) . The release time should be 10-12 months. Thanks.

Any update on the new version?

Multiple EasyEDA Instance are possible. There is an undocumented "feature", but it's not a bug either. Right-click on the interface and select the "New Window" option.Now you have a second instance of EasyEDA. **But keep in mind, they do not work synchronously !** 

@tmeschke, Thanks for pointing that feature out. It has always been possible to do this in EasyEDA: it is even possible to do this across multiple platforms. But as MikeDB and you yourself have pointed out in the topic above, the windows are not synchronised which makes this feature not only of little practical use but also makes it very dangerous because changes in one window are not related to changes in another. So for example doing **Update PCB...** in a window showing a schematic does not change anything in a separate window showing the PCB for that schematic. A  PCB tab will open in the same window as the parent schematic but the same PCB in the separate window must be CTRL+F5 refreshed before it will show any changes. Sorry but this is a recipe for disaster.