Consider this. Why is the knob there if you are not to change the tension. A manufacturer wouldn't put it there, would they?:D Get over it or when you really do need an adjustment you won't know how to do it. If you are fearful of this, ask a shop to teach you.
peace

I try to teach people how to adjust the tensions when they buy the machine. Half the time they don't take the time to learn. Some are too scared. Some assume it works so it will work forever.

Just turn it in very, very, very small increments and you will be okay. I had the same fear until I had no other option. Just go slow and small when adjusting.

I have learned to play with the tension on my machine so I have no fear of the top tension I did buy an extra bobbin case to play with and can also create some fun things that way so much to do so little time just don't get your 2 bobbin casings mixed up

The idea of a second bobbin case is good - I've suggested that many times. Going back and forth with various threads is doable much quicker that way - the upper tension would still have to be adjusted to go back and forth.

OMG, that's exactly how I feel. I hope if my tension needs adjusting, it's only the top tension.

I also have a fear of changing the tension. I need to get over it.

The trick is to turn it no more than 1/4 of a turn. I adjusted the tensions - yes both- for a friend the other day and the world didn't end. The machine did work and sewed beautifully. Hope this takes away your fear

It can come unscrewed - and if it falls into carpet - you may never find it again.

Do what ckcowl suggested- but also keep notes on what you did.

For the bobbin, I used "time" notation and whether I turned the screw clockwise or counerclockwise..
Example -turned screw clockwise from 2 to 3

I have adjusted the bobbin thread on several machines over time and nothing bad has ever happened. It's no use adjusting the top tension if it's not the one having the problem. I don't know who put the fear of a little screw in you ladies. Be brave - have a go_ just to get the feel of it. You can always mark the bobbin casing with a sharpie in case you want to take it back to factory setting. That little screw is there for a reason - to help you make your machine work at optimum level.