With the new High Output Powerplants, the tooltips in the research window do not indicate all that is needed in order to actually utilize the plants.
While it is obvious that Power Production is needed in order to get High Output Powerplants, the tooltips nor the format of the research window shows that Improved Efficiency and Powerplant Efficiency are also needed in order to actually use High Output Powerplants. You can research them, but you can’t use them until all of the underlying dependencies are fulfilled.
I guess what I would propose is to move Power Production up in the research window to be above Factory Expansion, then extend the line to double the length to put the High Output Powerplant into the third column. From there you could then draw a combinatorial line from both Power Production and Powerplant Efficiency to High Output Powerplant to indicate the need for both before you can even research the High Output one.
I do note that the Powerplant Efficiency tooltip does indicate it is needed for the high output side of things.