Is there a Better way to edit html template?

Hi,
to edit my html template inside the habpanel I use the edit mode (pensil).
In this mode a windows will open and I can edit the html but when the code is increasing this windows is not really pratical mainly because It cannot be enlarged at full screen and there is not row number.

Is there any other simple way to edit the html file at full windows and if it is possible also with row number?

Thanks
Lorenzo