Unfortunately it's impossible judge how many tiles are going to be in the next column, none of the objects are squares, they use the exact amount of tiles required to fit the full image - and since you have no way of knowing what that image will be until you build it, you can't know ahead of time what size it's going to be.For larger objects that have tens of tiles per column, you could even specify how many tiles it should place in one key press. Could use num keypad where each number would put down that many tiles in one go and judge object by object how many you would place in one click. You would only need to correct the bottom column ending in case of overflow.
You couldn't even have a system to auto place the next tile and manually move to the next column, as you have no idea if you need to start lower or higher than you did last time (since all objects are on an isometric grid it changes constantly). Plus wemade like to change their order constantly of how the tiles get placed. They sometimes also like to split the objects in to multiple sections, and have them overlay each other in chunks. Or leave part of an object to a different part of the library.
I don't believe there is any more efficient system available than what i've already added in this editor. Even if there was, we're 90% of the way there now, so any new system would be counter productive at this point.