The broth tends to be very low in density, it's basically water with a flavour, and I would like to make it a little bit more smooth and dense like a good pasta sauce; nothing like gelatin or something that will generate blocks or blobs, just a more dense preparation that will still retain the properties of a liquid or smooth sauce .
What can I use for this ?
You're very likely going to need a thickener, especially if you don't make your own stock. (On a side note - I highly recommend making your own stock at least once. You end up with a vastly different stock/broth when you do, and in this case, it might achieve the consistency you're looking for, because a good animal based stock has gelatin in it already.)
Gelatin shouldn't generate "blocks or blobs" when incorporated correctly, but if you don't want to use gelatin, you can also add corn starch, arrowroot powder, potato starch, tapioca flour, or other starch to thicken the broth. (Flour is an option, too, but I prefer other thickeners, since in my experience, it often takes more flour to thicken something, especially later in a cooking, and the dish takes on some of the flour's flavor and texture.)
Gums (the compounds often used to give non-dairy milks their creamier qualities) can also work. Xanthan gum is pretty easy to come by, though you may also be able to find guar gum. These usually only require fractions of a teaspoon, so shouldn't be enough to affect taste or most of the other properties of the broth except thickness.
For all of these, the usual way to incorporate them correctly, so they don't create blobs, is to thoroughly dissolve them in some water before adding them to the cooking pot. You'll want to use a whisk or similar utensil, to ensure any blobs are broken up.
If you want something more akin to stew, as opposed to gravy, you should only need to cook down the liquid in the broth for a while, or just drain off some of the broth when serving. The increases the ratio of vegetables and meat to liquid, which gives the dish as a whole a heartier and more filling feel, without actually making any of the components thicker. This is essentially how tomato sauce vs paste works -- the sauce has a higher water content than the paste. Because the tomato puree doesn't dissolve in the water, the result is a thicker or thinner solution. You can puree the ingredients in the soup (vegetables, meat, etc) to get a tomato sauce/paste kind of consistency.
A higher meat/bone to water ratio will result in a more viscous stock. Also, using the correct bones...those that contain the gelatin that will provide a better mouth feel. Finally, a long cooking time is helpful. I highly recommend making stocks with a pressure cooker. It dramatically reduces the time it takes and allows for an improved final product.
You can either work with some roux or you can make some dry mash potato. After the broth is ready whisk in the roux or mash potato as the broth slowly simmers. This is a very classical technique. I make bone broth for my wife all the time.i In make my stock then after I strain the stock I fry a mirequoix of veg then after I deglace with the white wine I reduce it right out back to oil then make a blonde roux over the vegetables. Add stock to make a veloute. Once you achieve the correct consistency add your whole garnish like kidney beans, pasta, green veg.
