newt is right - you have to carefully design your reusable logic and one glove doesnt fit all. If you want more flexibility, learn programming. Construct's event sheet is awesome, but it does have limitations compared to what you can do compared to godot for example.
The more flexibility you have - the more complexity and learning curve
The linearity in functions is not a problem at all - once it completes execution of whats inside the function, the process should continue from after the line where the function was called. Unless inside the function you haven't rerouted the execution to some other specific part of the game loop - which would defeat the purpose of the function - to be reusable.
My suggestion is to plan it out on paper first- say to yourself exactly how you want to structure it.
I personally try to make things modular, but have fallen in the trap of tangling myself in a mess in the past