Novellas are magical creations, compiled from multi-shaped bits and pieces, much like a Tetris game. It's up to you to fit the right pieces in the right spots. But novella Tetris pieces are multi-dimensional and sometimes don't conform to Euclidian-based geometric shapes.

Perhaps equating novellas to a futuristic Tetris/Rubik's Cube type setup is more appropriate.

Novellas have multiple parts, from the plot to the characters to the scenery and all the little fiddly bits linking them together. Each piece is shaped differently.

The characters have jagged edges that need to be ground down through drama and climax. The plot may be a bit squidgy in shape, distorting a bit as it molds itself around everything else, like a sentient blob consuming all that stands in its way. The scenery tends to stick colours and scents and sounds to the shapes, creating a kaleidoscope of sensations.

I've found several ways of handling all these shapes and colours and ridiculous rules of formatting and pacing once I know what my word count limits are: In this case, ~20,000 - ~50,000 words, give or take a sentence:

• Skip the red herrings and be willing to trim scenes or chapters, or even characters, depending on how far over the word count you happen to be.
• If need be, I'll trim out subplots, tossing them in a bin for later pokage. I just need to be careful with them as the bin tends to fill up fast...and gain sentience, with delusions of grandeur. And as fun as global domination is, I'd rather not have to bow down to discarded plot-fodder if I can help it.
• Unlike Tetris, getting everything to fit in the right place won't make the words disappear. That'd just be disastrous. But, it will make your words more powerful. Not in the global domination type powerful. More in the easier to read and more effectively conveyed type powerful.