Plants have different options what to do with the glucose they produce through photosynthesis. Producing lipids requires a bit more energy, but has the advantage of more stable storage form (bacteria can’t digest fat), so plants only produce lipids in large quantities when they have enough energy. Actually animals store surplus energy as fat as well. For humans we call that obesity.

https://www.britannica.com/topic/fat/Synthesis-and-metabolism-in-living-organisms

So to reach this step we need to make sure plants have that surplus of energy by feeding it in the most efficient way. That is through microbial metabolites and not through salts and ions, I usually imagine it with ready made building blocks compared to raw materials.

This is a natural process, but since we mess up photosynthetic efficiency and hinder microbial life we usually don’t reach lipid production in the quantities we need for healthy plants.