Methods:
INVENTORY.pushItems("turtle",slotInChest,Count,slotInTurtle)

or

Could just add an optional SLOT param to turtle.suck methods
turtle.suckDown(Count,chestSlot)

Would allow more flexibility for inventory management with turtles

The inventory transfer methods are very much tied to peripheral and wired networks. I don't think it makes sense to start adding new magic identifiers.

If you just need to transfer items to the current turtle, you can use peripheral.getNameLocal to get its name on the network.

But in the case the turtle is not a network, that makes this way impossible, i just want to have a turtle going back and forth between chests but be able to use trhe chest methods instead of turtle.suck() because of the better control.

You can wrap the chest and move the target item to the first slot of the chest and then use turtle.suck().