@pindac The tool is audio recordings of one’s system from the listening chair position/location. You use this tool, the audio recordings, to make assessments and them you make adjustments to yield improvements to the sound you hear in the room.
Not only digital crossovers can be adjusted and tweak. In my OKTAN6 six-way horn system, I make adjustments to the Finemet transformers based crossovers to change the resultant sound at the listening position.
It just takes a reiterative process to fine tune the resultant sound the sound that you are targeting in your head. There are a number of methods to make adjustments, the adjustable crossover is just one of them. As you mentioned, making changes in the digital domain is another way, and technically the most precise and least subtractive way of modifying the resultant sound.