Tallow is a resource used by only one building (in conjuction with Herbs, which are either not realistically guaranteed or not available on your map at all. Wax was previously only used by one building, but a Tech talent made it give Barrels a bonus. You’re going to spend your game dumping Tallow in the hundreds, especially in your endgame.
Without turning to a medieval expert, I looked at Wikipedia for some uses for tallow and will suggest some period-appropriate uses for it.
Tech:
Can be used in buildings that use Heavy Tools as a lubricant, to decrease the amount of work needed to produce a resource. This reflects both a productive bonus, and increasing the amount of resources a single Heavy Tool can produce before expiry. This would be a Tech, as the cited use irl was in piston steam engines, and it can be imagined that the settlement first innovated the use long before other societies without being too anachronistic.
Can be used by Fishers to increase their yields (perhaps with the prerequisite of the Fish Replenishment Rate tech)
Resources
Luxury Clothing, if Sheep are released, can be made using both Wool and Tallow (perhaps other resources too, representing dyes). This represents the use of Tallow as a lubricant, strengthener, and softener in yarns.
Animal Feed
Tallow was used in the making of animal feed for dogs and pigs. If pigs were ever introduced into the game, pig farmers could prioritise Tallow for their feed for livestock that can use a smaller space and be less dependent on fodder quality.
Edit: 871 created in 12 months, and 2 full Soap Shops only use 145. That would require fitting 10 more Soap shops somewhere, and then will be deleting tons of Soap because it would be impossible to sell even with the tech that gives traders more gold & economic monument
In the game, we often need to manually delete items like fur, animal fat, herbs, honey, and wax. Could you design an incinerator? This would send resources exceeding our set quota to the incinerator for burning, eliminating the need for manual deletion.
The excess tallow problem is because you can’t limit it without also stopping the production of meat. If that was addressed then this whole conversation becomes irrelevant. I do like your ideas for other uses of tallow.
Let’s not forget the chandler as a user of tallow. This is the most obvious solution.
Tallow candles were the kind used primarily in antiquity, not beeswax ones, which were saved for special occasions or altogether unaffordable. Tallow candles would give off a black sooty smoke and something of an odor, but were the most easily supplied indoor lighting in peasant homes etc, excepting rush-lights, which were just rushes dipped in flammable oil (again, probably tallow or otherwise pitch if available) and then lit up for a short burn.
So, your chandler then, could make beeswax candles for trade or for supplying luxury homes, and tallow candles for the commoners. Like a fletcher, you could have them produce both types in varying ratio based on what you need at a given moment.
I am a strong proponent of adding a pigsty so one can use an overabundance of food or spoiling food to fatten up pigs, from which then both meat and tallow/lard can be harvested.
That would probably require the pigsty to automatically collect foodstuffs below a certain spoilage threshold to turn it into pigfeed. After all, the main advantage of pigs is, that they don’t use much space and basically live off food scraps, making them a very economical way to get rid of food waste and convert that into good, fatty meat.
It’s not exactly sensible that the only source for tallow is wild game, when pigs were prized and raised for exactly their fat throughout the world.
Also it would be great if Pig births didn’t work by the annual Livestock timer, but instead was based on the additional food that came in. Have Pig Feed made with resources like regular feed for basic viability, then from Tallow mixed with spoiled food and a small portion of nearby Waste produced (food garbage) coming in, have it fill up a bar which produces a new Pig once full.
This would allow Meat from Pigsties to be produced more evenly across the year to allow Smokers more even access to Meat similarly to Hunter Cabins.