Spawn a Villager with Custom Profession

In the villager custom profession tab there isn't a spawn parameter that regulates the possibilty of a villager having that profession. So i figured i could do that by replacing the other workstations with a custom block, but neither the procedure or the block generation doesnt work. Is there any way to make those types of villager spawn?

https://i.postimg.cc/sxFNF160/image.png

https://i.postimg.cc/6Qwgq7BT/image.png

https://i.postimg.cc/mkb7Fstg/image.png