Segno Variation ("Serpent") should be on barline, not above
The alternate segno sign in musescore is shown incorrect.
The sign mustn´t be above the stave (like a normal segno) but attached (or overlayed) to the bar line of the bar it´s reffering to.
So the alternate segno must be shown more like a common repeat sign (or an akkolade) instead of a normal segno.
Once attached to a bar, it has to attach to the barline of the actual bar throughout and down the whole socre. (For it´s a system sign)
The upper and the lower end of the serpent must overlap the lines. (A size of 30 was alright in my case, but I had to attach it manually (not with strg + downarrow) because it wouldn´t have been symmetric.)
Like an akkolade the serpent would be stretched lenghtwise accross each voice of a register only interrupted if the register changes.
So maybe the code of musescore can combine the "jump features" of a normal segno with the layout characteristics of a repeat sign (akkolade). (Only with the serpent "winded round" the bar line)
This issue has already been mentioned in a 2014 thread. But hasn´t been executed so far. (The alternate segno still is nothing but a different design for a normal segno)
That´s the only way I know this sign is meant to be used (I never saw the serpent above the staff)