long, dangling, kerchief, rope
纚 centers on something long and hanging loosely, like a dangling rope or a trailing kerchief. The meanings 'long', 'dangling', 'kerchief', and 'rope' all share this image of a flexible, extended object that hangs or trails.
纚 combines the thread radical 糸 with the phonetic component 麗. The character originally referred to a long, trailing kerchief or cord, with 麗 suggesting both the sound and the idea of something extended or beautiful.
The thread radical 糸 on the left suggests something made of fibers, while the right side 麗 (which can mean 'beautiful' or 'elegant') looks like a long, flowing garment. Picture a beautiful silk kerchief or a long rope dangling elegantly from a thread.
For シ, imagine a long, dangling silk rope that looks like the letter 'C' (シー) as it hangs in a curve. The 'C' shape cues シ while the rope dangles from the thread.