It isn’t the mountains ahead that wear you out,
it’s the grain of sand in your shoe.
Sometimes it’s just a small detail that can make you crazy, and with Scrivener’s fullscreen (or now: composition mode) it was the typewriter scrolling. When activated, the line you work with is automatically the vertical center of the screen.
If you are writing the text from scratch, this feature is very useful — you can fixate the same line with your eyes and do not need to go down-down-down until the text is the the very last line of the virtual page (like in Word). But it can drive you crazy if you are editing the text and whenever you type somewhere it is automatically recentered vertically, thus forcing you to visually jump to the vertical center each and every time you change something.
Luckily there is the Format – Options – Typewriter Scrolling Setting in the menu bar, if you disable it, Scrivener does not show this behavior — in the selected view mode. What drove me mad and took me a while to understand is that there are independent settings for the normal window and for the composing/fullscreen mode. Thus, you have to disable Format – Options – Typewriter Scrolling in the composing mode independently from the normal mode, either by going with your cursor to the top of the screen, or by pressing ctrl + cmd + t when in the composing mode.
As you usually do not see the menu bar in the composing/fullscreen mode, it’s easy to miss it.