Greetings,
it would be great if you could, when Factorio let you do it, add the option to put signal cables onto the Loaders. I tried it because i want to set up my Tree Farm and prevent the seeds to unload under 1500 Seeds, to have a self planting tree farm (Factorissimo + Robot Tree Farm + Warehouse) and can use the leftovers as fuel, but at the moment i can only use inserters. Which is not a nice option for me.

loaders dont have connection points .. base game dynamics .. one option you have is to connect your circuit wire to the belt attached to the loader and put your conditions there.