I uilt a bloc in my extention with multi parameters.
I would like help the use of this bloc by choosing a prefilled bloc like this
what have i to had in my code to do this ?
You cannot do that for extensions as now now. Only the internal components has access to that feature.
Instead of letting set all this up, take all the data, return it as a dictionary, and let the user decide which data to use.
If you plan to later publish your extension, remember the naming conventions
Taifun
I planned to have one function which return all data, an an other with only those interesting or user in order to opimise computing time...
Yes you're rigth, I always forget it ! 
ok. so no way to make it more usefull...
Maybe you can use the helper block to do so.
But returning all data in json format is the best solution I think.
ps: or you can return all data in an Event block with many parameters.
following your remarks, I did some tests, and the time saving is negligible compared to sending a list with all the information (around 2ms)
so I abandon this idea and just provide a list with all the info.
I will update the post of my extension according to this