Set the scene height x width?

Does anyone know how to change the canvas size height and width (scene) without changing the proportions of the drawing?

If the bitmap layer already exists, select it and go to menu-Drawing-Change Bitmap Drawing Resolution

If you have not created the layer yet, go into menu-Scene-Scene Settings…
and go to the “Drawing Resolution” tab to change it globally for the entire project.

If you want to set it for all future projects, go into the preferences and on the “Drawing” tab
at the bottom off the page you will see it is limited to 200% of the project resolution by default.
You can increase or decrease this percentage to have all new projects you create use this setting.