This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
緫 combines 糸 (thread) with 怱, which likely contributes a sound element. The exact historical development is uncertain.
The left side is thread 糸, and the right side 怱 looks like a hurried heart. Imagine threads tangled in a rush, but without a clear meaning, treat this as a visual placeholder.
For ソウ, imagine sewing (ソウ) threads together quickly: sew -> ソウ, and the thread 糸 is being worked in a hurry.