Some good questions waiting for answers.

[makubexmastr]

1.Is it possible to make 2 different effects in one single skill?
2. how do you make a loading bar for cool down effect?
3. How do you make an item/skill that can give the hero holding it: converting attack % to both health and mana.
4.How to convert neutrals/normal creatures(except heroes) into mana/health/gold, while instantly killing target enemy creature?
5. How do you change the trigger variables inside a common skill without using jass(no time to study jass, too busy >_<!!), turning it into a custom skill?(except for the change icon and others.)

 

[TheLegend]

1. Use buffs: Create two buffs doing what you want them to do and add the buff's to the target of the spell. Once the spell is done remove the buff's
2. With floating texts and timers: The timer is the length of the cool down and the floating text the graphic value. Its best this way... store the cool down as a real value (ill use cd)... start 10 timers each one having a greater cool down by cd/10. Once the first timer expires its like it's been 1/10 of the cool down time so change the floating text (eg: IIIIIIIIII ) when the next expires set the second "I" to red and so on...Just make sure you remove leaks (the timers and the floating text)
3. You can do this using a trigger... add a buff when the hero gets the item (remove it when he drops it) and in a trigger use the Event - Unit deals damage. In condition check if the triggering unit has the buff and add 10% of the damage to the units hp and mp
4. I don't get what you want here... bounty?... a spell like the one arthas has (i cant remember the name) when he heals himself using by killing his units
5. What are you looking for?

EDIT
Ok i did some triggering and I must say this...learn JASS. The question 2 cannot be done efficiently without jass cause the cool downs overlap and you cannot detect the cool down with GUI so forget it...

 

[annihilator127]

Alchemists can use the ability Transmute, which kills an enemy or neutral unit and turns it into gold. To add health/mana you can use the trigger action 'Unit – Set Life/Mana (to Value)'

 

[keychup]

1: Yes. Everyone does it.
2: Use floating text. You can learn how from Blizzard's Skibi Map. There's a hero who builds towers which have loading bars for mana.
3: Get a passive buff placer and put it on the hero/item.
Event: "A unit is attacked"
Conditions: "Level of Ability is Greater Than or Equal To 1"
Actions: Wait for Condition(Attacked unit has buff) checking every 0.10 seconds.
Cause Attacking Unit to Damage Attacked Unit dealing (X%*Max Life of Attacked Unit) of
attack type Hero and damage type Normal
Though I recommend you not to use it because you'll need multiple bars to display the cooldown for each ability.
The Trigger you are looking for is
4: Get a single-unit target ability
Event: "A unit Starts the effect of an ability"
Conditions: "Ability being cast is Equal to Ability"
Actions: Set Player(Owner of Casting Unit) Current Gold to (Player(Owner of Casting Unit) Current Gold)+(X%*Max
Life of Attacked Unit)
Set Life of Casting Unit to (Life of Casting Unit)+(X%*Max Life of Attacked Unit)
Set Mana of Casting Unit to (Mana of Casting Unit)+(X%*Max Life of Attacked Unit)
Cause Attacking Unit to Damage Attacked Unit dealing (Max Life of Attacked Unit*10) of
attack type Normal and damage type Normal
5: Open Trigger editor and press Ctrl+B You can put all the variables you want there. It will initially be empty because a Melee Map doesn't use variables (except Regions).

EDIT:
2: If you can't find the trigger on skibi try this. Last April I made some heroes with Rage Bars. Just download the map, open it then choose any hero which are tagged "Warrior Class". Try studying it and maybe you could use it to make your own cooldown bar. It's discontinued and I never got to finish the whole map so don't ask ^_^.

The Trigger is called Rage Bar btw so just press Ctrl+Shit+F and type in "Rage Bar"

 

[TheLegend]

you can easily make loading bars when you know its time... but you cannot detect cool down...

 

[keychup]

no, but there is no way to reduce cooldown either. so if your ability's cooldown is 10 seconds you can always set the timer to 10 second cooldowns. if you have a cooldown that becomes less with each level you can use arithmetic to calculate the ability's cooldown. if the cooldown was forced to reset then you can detect when the cooldown was reset and make the bar empty instantly.