Merge branches with selected indices

[BIM_design]

Hello!

I am a beginner in grasshopper and I have some problem with merging trees.

I have 2 lists (with numbers -45,-69 and -57,-57) that I would like to combine into 1 list but I want to do it in specific way. Above these lists I have 2 panels with indicies that indicates branch number in combined list.

How can I achive it?

[inno]

a GH file is always better than a screenshot

[BIM_design]

Thanks a lot! I will remember to attach gh file next time