Inside our Microsoft Dynamics CRM instance, we've got a section which is taking 1/3rd of the space inside the form editor:
After saving and publishsing this, it takes 1/3rd of the space on the rendering output along with trolls of scrolls:
How to make a section take entire space in Dynamics CRM form editor?
In the form editor, select the Tab (not the section), and click "Change properties".
Then in the formatting tab, select "One column", and finish with OK.
Finally, save and publish your form and it should fill the entire space.