Thank you very much. :)

That exactly what I was searching for. 

Is it possible to fix the size of the new window ?
When it open a habit task, because of the logbook, the new window is soo
big that it make the agenda no more visible.


Ihor Radchenko <yantar92@posteo.net> writes:

> Sébastien Gendre <seb@k-7.ch> writes:
>
>> Is there a way for Follow mode to automatically narrow to task it show
>> (and its children headings/tasks) ?
>
> See `org-agenda-follow-indirect'