One of the more useful tools in Lightroom is “Clarity” which boosts the edges of the picture, especially in the midtones. However, a clarity slider is conspicuously absent in darktable.
However there are two ways to get the same effect.
Option 1: Local contrast
One alternative is to use to the local contrast module, which has a very similar effect to clarity.
Option 2: Use the clarity preset in the Equalizer module
The equalizer module occurs in the Corrections group (you may have to activate it – click on “more modules” at the bottom to find it).
Under the presets you will find two clarity options: “clarity” and “clarity – strong”.