You can combine gravel and dirt to make coarse dirt.
You can combine gravel and sand to make concrete powder.
So shouldn't you be able to combine dirt and sand to make something?
But what purpose would the thing serve in-game? (Every addition entails some overhead, so adding something without a purpose is not desirable.)
Continuing logically, one would expect the product to be sandy soil; possibly something roughly equivalent to potting soil.
However, there are already several 'soil' types [very loose definition] in MC: dirt, coarse dirt, sand, gravel, 'grass', mycelium, podzol.
Flowerpots already work without explicitly adding a growth medium, so possibly this could be placed in cauldrons to make larger planters – but what advantage would this offer to simply letting current soil types be used?
You've identified an obvious opening in the crafting recipe space, but adding an item using that 'missing' recipe requires that some sort of purpose be served by the addition. "Looks cool" is not generally considered sufficient. [The item/purpose should also have some connection (even if only by MC physics) to the reipe….]
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WARNING: I have an extemely "grindy" playstyle; YMMV — if this doesn't seem fun to you, mine what you can from it & bin the rest.