hi !
i'm disapointed about the grid of Kibana's dashboard.
Why it's not possible to resize precisely all visualizes in dashboard ?
Can i modify the grid's step size somewhere ?
My kibana's version is 5.6.9.
Thanks.
Starting in 6.3, the grid is much more fine grained to give you more control over the size of your panels on a dashboard. Unfortunately there is no way to customize it in your version.
Thanks again Stacey !
This is the answer i was searching.
Too bad about my Kibana's version 
I'll trying the new one when it will be "current" status.