To simulate wieghted random numbers in GDevelop, you could create an array with each number being added the number of times according to it’s weight, and then picking a random array entry.
So, say the weightings are 1:1/10, 2:4/10, 4:3/10, 5:2/10, then the array would end up looking like:
[1, 2, 2, 2, 2, 4, 4, 4, 5, 5]