When you practice your lag putting indoors you train and develop a skill that is really useful on the course. Many low handicap golfers know exactly how far they are from the hole by stepping off the putt. They then take into account the elevation change and break to create an "effective" distance based upon how fast the greens are rolling.
For example there are a number of putts on hole 9 at Alpine Country Club that can be level, severely uphill, or severely downhill. I'll step off the putt distance, say 10 steps or 30 feet, and then if it is uphill I may need to add 80% to that is an effective 18 paces. Downhill can be the opposite. A 10 step putt may play a 5 or even a 3 or 4 depending upon the speed of the greens on a given day.
So I always try to feel how many "level" steps of speed a putt needs which can be quite a bit different from the physical distance to the pin. And when I practice lag putting with Trackman I can really work on what a 5 step putt feels like or a 10 or even 25 step putt. This is measured over and over again and gives me a gauge that I can take to any course. I simply adjust for a given quickness level of the greens on a course, line up, and let it go. The practice I have indoors on the lag distance control directly correlates to lag distance control success in the outdoor game for me.
So here is a video showing how you setup all the different scenarios on lag putting distances with elevation changes in the practice range section of Trackman performance studio.