Any sort of soft or springy material is unusable to create friction. The reason is simple: elastic deformation and load stress fail due to plastic deformation / sheering.
Basically if you'd use e.g. foam when load gets applied it will deform but try to get back into it's original shape. Thus the control will feel mushy. You can move it but it will have an effect of springyness.
For something like the signal stalk you don't want analogue positioning though. So using the techniques for throttles is not delivering the best results.
For your specific case I'd recommend notches and a spring loaded roller to lock it into position. You can 3d print this. Alternatively you could use a real signal
That said, a normal turn signal returns to position on wheel rotation. That'd be a complex device to craft so I suggest, if doable, to just use a momentary switch like done here:
https://www.youtube.com/watch?v=k5ky446ns2II hope I didn't misunderstand you completely - sorry if I did - I'm not a native speaker.