I kinda think any input node (vector, RGB, value, etc) is essentially a variable. You can change them as needed and use them when and where you want. Like if I had a game that used a float variable called health, and if it is ever equal to 0, do something (game over). But you can use an float input to check if the z position of a bunch of verts is above or below something, then do something (delete or move). Inputs aren’t really supposed to be arbitrary values. They have meaning to what you are doing and what result you want to achieve.
