every 20 seconds create object Marker at position
x= random(0,LayoutWidth)
y= random(0,LayoutHeight)
on player collission with Marker
set marker instance boolean collected to true
set marker position to
x= random(0,LayoutWidth)
y= random(0,LayoutHeight)
on player collission with Marker
and
Marker instance boolean collected = true
add X to variable currency
destroy marker
or if you want to create the marker at predefinde positions
you could place invisible spawner sprites and use pick random instance
and spawn at placeholder instead of the random position.