itch.io

Creating a buffer with "var" does not matter, it is still a memory leak if you do not destroy it.  Having it created every single frame in the draw event is going to be much slower.  If it does not move then create it once and freeze the buffer.  If it moves you can create it, use and then destroy it.  Or use primitive drawing if it provides the right format for the vertex...I'd have to check.  

When you create any type of dynamic memory such as buffers, ds_lists, other ds structures, or surfaces, they are in memory until you destroy them manually.  Declaring a local variable with "var" only holds a reference to the memory, it still exists and still needs to be managed or you'll have a memory leak.  Even vertex formats can be destroyed, but those usually are very tiny and you make a couple that never need deleted until the game closes.

Note, that if something uses memory that will always persist until the game closes then you really do not have to destroy it.  When the game closes the entire heap will be freed by the OS.