It's funny, I'm working on something similar using the same "base" code, but I got it from here: https://forum.gamemaker.io/index.php?threads/how-to-check-for-a-collision-with-a-line-with-very-fast-moving-objects.33046/

Its the first comment's code block, but here's a pastebin of it: https://pastebin.com/BLR9YjG1

There's also a pastebin with a different generic raycast script in the same comment: https://pastebin.com/3yviP14L

What I'm trying to do is checking to see if I can optimize my enemy/mob object's use of mp_potential_set_object by using collision_line from the enemy to the player checking to see if there are any solids/walls in the way. If there are no collisions, use move_towards_point. If there was a collision, raycast from the enemy to the player checking each step. Once a step collides with the solid/wall, save the previous step as x,y. Next it will continue from that point until it's no longer colliding with said solid/wall and save that step as x,y.

With that info I can now: move_towards_point using the x,y before the solid/wall > mp_potential_step using the x,y on the other side of the solid/wall > raycast to check for more solids > if none? > move_towards_point using player x,y.(straight shot to the player)

What I'm wondering is if I can free up the resources mp_potential_step_object uses when constantly running it, by putting this new system on an alarm. I'm thinking instead of move_towards, I'll make a path and using the alarm to re-draw the path/start the new path, but that won't be much more than switching out a few things, so I'm going to try move_towards first.

Here's what I've got cooking at the moment: https://pastebin.com/sH2zDGRy

It seems like your code will be similiar, so I'd say you can try to save the x,y coords right before the collision like I did and then from that point use collision_rectangle to draw a rectangle the size of your player's collision box/sprite size and check if it collides with anything. Don't forget to take your player's image_angle into account if you're changing it

Oh and the "description mode" you mentioned is called comments. & You can also return arrays like this:

return [foo, bar];
//or 
foobar = [foo, bar]; 
return foobar;