Nice Pic !!
Yes they do use some threadlock but its not permanent … just needs a bit more muscle.
There is some info … About moving saddle back … which also may help…
strida.us/Tips-from-Mark.pdf
I played about trying various saddles … I like soft saddles that sit low on the seat mountings so they look part of it, rather than ‘plonked on top’ … but seats are SO subjective !!
Once you get the screw undone … slide it out (you may have to bend the flexible side of the saddle to get it to go past. You may need a flat screw driver to carefully prize out the saddle rail on one side. Then you can snap on a new saddle – rails into the slots, one side at a time seems to work best - but also possible to snap on straight down.
The main factor which would prevent a saddle fitting is if the top is horizontal or not (there is no angular adjustment on the plastic strida seat mounting). If the rails are a tight fit in the slots that is OK, as when you refit the bolt and clamps the rails will be pulled into the relatively soft plastic grooves. BUT DO NOT over tighten the screw / Nut … just take up the space, close the gaps, BUT with NO overall high clamping force. This is to prevent damage to the seat mouldings - the only reason these ever break is due to over tightening this bolt/nut … it acts like a vice and crushes the plastic, which is then weakened. Other wise I find the plastic (nylon) seat mounting is virtually indestructible (and is low cost to replace if necesary).