Some note types (such as Text and saved search) intentionally limit the width of the content.
This might appear surprising at first, but the idea is to make text fit well on wider screens without appearing distorted. This is especially the case if the document contains Images, tables or other width-dependent elements.
The content width is expressed in pixels and can be changed from Options → Appearance → Content Width and adjusting the Max content width section.
To effectively disable the content width limitation, simply set the width to a value larger than your screen size (e.g. 9999).
By default, the content is aligned to the left, but it can be centered horizontally by checking Keep content centered from the same section as the content width.
For notes with large elements such as Tables, it sometimes makes sense to avoid the content width without affecting other notes. To do so:
On a shared page, a text note is
shown at a fixed reading width, whatever the width configured in Options,
and the navigation tree, the content and the table of contents are kept
together in a column centered on a wide screen. A note with fullContentWidth,
or of a type that is full width in the application, uses the whole width
of the window there, with the navigation tree and the table of contents
at its edges.