First just realize that you need 5Xthe number of rows up you are.
You need to keep the number of passive point listed invested in the tree below each “tier” of passives. So if you wanted to change a passive in the first row without removing any from the second row, just make it so you have more than 5 passives invested IE if you have 6 invested in the bottom row you can remove 1. If you had 7 invested in the bottom row then you can remove 2. Now if you points in the 3rd row and say none in the 2nd the same rules apply. The numbers in red are just how many TOTAL point need to be invested in the tree to unlock that “tier” of passives. So for the final row you need 45 passive points invested. These 45 passives can be all in the bottom 3-4 tiers and you would still have access to the top node it does NOT need to be 5 per row just needs to be the total listed.
Will tell you how many passive points you have invested.
To summarize as long as you have more passive points invested in the rows below your HIGHEST “tier” of passives you can reset node until you hit the number in red.