Adding triple jump to your engine

 playerJump script

if (place_meeting(x,y+(global.grav),objBlock) || onPlatform || place_meeting(x,y+(global.grav),objWater))
{
    vspeed = -jump;
    //djump = 1; <--replace this line with this one:
    djump = 2; //give 2 jumps back
    audio_play_sound(sndJump,0,0);
}
// else if (djump == true || place_meeting(x,y+(global.grav),objWater2)) <--replace this line with this one:
else if (djump > 0 || place_meeting(x,y+(global.grav),objWater2)) //lets you djump if you have at least one remaining
{
    vspeed = -jump2;
    sprite_index = sprPlayerJump;
    audio_play_sound(sndDJump,0,0);
    
    if (!place_meeting(x,y+(global.grav),objWater3))
        //djump = 0; <-- replace this line with this one:
        djump-=1; //remove one from djump counter, allows you to djump again later if you still have one
}

 player collision with block

if(!place_free(x+hspeed,y))
{
    //left/right collisions with block, removed for brevity
}
 
if(!place_free(x,y+vspeed))
{
    if (global.grav == 1)
    {
        if(vspeed <= 0){move_contact_solid(90,abs(vspeed));}
        //if(vspeed > 0){move_contact_solid(270,abs(vspeed));djump=1;} <-- replace this line with this one:
        if(vspeed > 0){move_contact_solid(270,abs(vspeed));djump=2;} //set djump to 2, giving you two djumps back
    }
    else
    {
        //if(vspeed <= 0){move_contact_solid(90,abs(vspeed));djump=1;} <-- replace this line with this one:
        if(vspeed <= 0){move_contact_solid(90,abs(vspeed));djump=2;} //set djump to 2, giving you two djumps back
        if(vspeed > 0){move_contact_solid(270,abs(vspeed));}
    }
    vspeed = 0;
}

if (!place_free(x+hspeed,y+vspeed)) {hspeed = 0;}

 scrLoadGame Script

//Only applies to the YoYoYo Engine!
//Allows you to triple-jump immediately if you saved in midair

//find this line:
global.player_djump = 1;
//and replace with this:
global.player_djump = 2;

 scrInitializeVariables Script

//Only applies to the YoYoYo Engine!
//Allows you to triple-jump immediately if you spawn in midair

//find this line:
global.player_djump = 1;
//and replace with this:
global.player_djump = 2;

 scrKillPlayer Script

//Only applies to the YoYoYo Engine!
//Allows you to triple-jump immediately if the player dies and a new one is created without loading, and is created in midair
//(yeah it's a contrived example but I'm just including it for completeness Keepo)

//find this line:
global.player_djump = 1;
//and replace with this:
global.player_djump = 2;