copying last section for left side/right side

[pixelbackwards1]

i've always wanted to have this in js engine until months later, here's a reason why

charting a specific song that has for ex. spam charting on the left side and normal charting on the right side

sorry for this being too short and low effort!!

[JordanSantiagoYT]

there's already enough buttons in the section part, why add another 2

and uhh there's nobody whos done a chart editor tab with a subsection/extra page