Actually, in some industries this is actually a good thing
If you can have a bumpy first day on Friday, and e.g. the warehouse is closed on the weekend, you can fix all the things you've seen on Friday during the weekend. And don't have to suffer through a real rough week with in-production patching
IMO there are no harmless ones (by that I mean dictionary definition superstitions - not just things like traditions and adages that have a logical reason or basis), if a person truly believes in actual magical thinking no matter how silly it's a doorway to accepting the rest.
Like letting in bullshit like horoscopes, homeopathy, faith healing, yearning for eschatological prophecies...
If I've been a good boy my poop session will go smoothly. If I think I was a good boy, but then my poop is awful, I think "damn I must have done something...". If I have been an asshole, but my poop goes well, I think "wow, I'm gonna have to pay this back tenfold tomorrow!"
If you hand someone a sharp object like a knife or scissors you will soon get into an argument. Gotta set it on the table for them to retrieve instead.
If someone says something bad, knock on wood. Like "Well X thing could happen" where X is like. A storm, the cats learning how to tap dance, a river exploding. Knocking on wood to make that not happen.
Whenever I get out of my car with lights still on and it dings to warn me, I thank it for reminding me. I just know the day I don't do that is the last day that ding will happen!
I do a monthly newsletter at work. I collect the stuff for the newsletter in an Excel sheet. I normally end up with around 12 items or so. But that makes my Excel sheet stop on line 13 because of the header row. So I'll add 2 more things. Because if I just add 1 then it will be 13 entries. So my newsletter will have less than 11 or more than 14 entries. I don't know why, I don't care about the number 13 anywhere else in my life.
When I hang my clothes up on the line to dry, I have to use matching coloured pegs for each item of clothing. I like the symmetry. It feels wrong to do it otherwise.