Sometimes, before I have automated a production line, I have a few items in my crafting queue, e.g. a bunch of Science Pack 2. Then I realize I'm missing a few pieces of transport belt.
I'm aware that it's the purpose of the game to automate everything, but is there a key combination or shortcut to push crafting jobs to the front of the crafting queue?
Unfortunately no there isn't. I've also searched through all the mods on the forums, and haven't found a mod that does this either.
The only thing to do is cancel everything in the queue (you can do it quickly by shift+left-clicking several times on the first item-slot), then queue everything in the order you want. You don't lose any items this way, unless your inventory has become full since you placed the orders (in which case, the extra items get thrown on the ground... so make sure you're not near any conveyors when you do it!)
Another option (assuming you're near power) is to just throw down an assembling machine, manually fill it and have it build what you need, then pick it up again.
A mod was recently released for this: https://mods.factorio.com/mod/QueueToFront
