Question: I am using your Step by Step Novel Planning Workbook to plan my Novella. I'd like to know if I need to simply adjust anything because I'm writing a Novella, instead of a Novel. In other words, are there any story arcs that may be cut out because it will require more words?Answer:
The short answer is no.
The long answer...
How many words it takes to illustrate an arc depends somewhat on your writing style -- how verbose or hard-boiled it is.
Some novellas will develop all four of the major throughlines. The difference might be that some or all of the signposts may be single events rather than sequences. Or some throughlines may be more fully developed than others. The scale of the story may be different too. For instance, you might write about a briefer period in the main character's life.
It also depends on the type of story you are writing. Some stories (e.g. plot-driven) put the overall throughline in the foreground and the others in the background. Others (e.g. romances) put the relationship throughline in the foreground and the overall throughline may receive less emphasis. A character-driven story might put the main or impact character throughline in the foreground, etc.
That said, you may choose to have fewer subplots concerning minor characters in a novella than you would in an epic-length novel.
Best of luck.