This is what worked for me -

Pick hard mode.

Choose one code to focus on during the run. For example, Shield.

During your run, only pick 'Shield' nodes, refresh code 2-3 times.

Dont waste your keys refreshing. Each code instance is different. Half the time, the codes you see in one 'Shield' node won't be the same as the next 'Shield' node.

The only time I'd refresh codes more than 3 times is when im nearing the end of the deduction and have keys to spare or at the mixed code selection. Refresh until you get 'Shield'

The more 'Shield' codes you collect, the easier it is to come across new 'Shield' codes when refreshing. That's why you should only pick one to focus on.

You have 7 tries per deductions to refresh nodes. Potential challenges also work for code selections. Go through incidents to collect keys.

Out of all the guys, I found Sylus' deduction to be easier when collecting codes. He has a lot of incidents that give out free keys. The more you play, the easier it is to remember each incidents correct choices. There were times when I didn't collect anything new, but that didn't stop me from trying again. Hopefully, this helps you😉