Where the shape comes from
A hand 又 holding up a cut stalk — the top stroke is half of the bamboo 竹. From the branch itself came the sense of anything that props something up, then a sum branched off and paid out (支付), and the measure word of 一支笔. Barely any characters are filed under it, but it gives both sound and sense to 枝 "twig" and 肢 "limb".
汉字 filed under 支
No published character on HSK Guide is filed under this radical yet. 汉字库.