TL;DR
In the technology research screen, arrange the technology icons in columns instead of by rows. The highest level science pack required to research a technology determines which column that technology appears in.This suggestion is an enhancement of the reordering of technologies based on cost that was applied in Factorio 0.15.
What ?
Here's some example mock-up screenshots. The first one is what you would see at the start of the game, when no technologies have been researched yet:This second mock-up shows what the technology list could look like part way through a game. This is a situation where the column based ordering makes it easy to browse and choose a low cost technology to research next.
The suggestion is to arrange the list of technology icons into the following columns:
Column 1: (Red) All technologies needing only science pack 1.
Column 2: (Green) All technologies needing science packs 1 and 2.
Column 3: (Blue) All technologies needing up to science pack 3.
Column 4: (Gray) All technologies needing up to the military science pack.
Column 5: (Purple) All technologies needing up to the production science pack.
Column 6: (Gold) All technologies needing up to the high tech science pack.
Technologies requiring space science (infinite research) currently don't show up until unlocked, and I see no need to change this. These technologies could be added to the bottom of the high tech science column.
Why ?
When you are producing multiple types of science pack, you have a broad choice of technologies to research. Often you might want to research a number of low cost technologies before committing to a high cost technology that will be slow to research. With the current row based listing, a low cost technology like Grenade Damage 1 can be half way down in your list of available technologies behind a more expensive technology like Nuclear Power, just because of the different science pack mix. In contrast, with the column based display order you can just scan across the top few rows to see which low cost technologies are ready to research.The columns also provide an easier preview of what technologies will be available when you unlock and start producing a new type of science pack. This may provide an increased incentive to progress up the technology tree.
There is an additional benefit for color-blind players: They can tell the highest tier science pack required based on the column the technology is listed in, without having to distinguish the colors of the science pack icons.
Note: The ordering in my example screenshots is based on the current in-game ordering. I've just transposed from row based to column based, transitioning to a new column when a new science pack is required.