There is an increasing number of aircraft around the airport with "all-glass" cockpits and no analog backups. Modern electronics have reached a level of reliability where this is now reasonable. Things can still go wrong though: A battery fire, smoke in the cockpit or other problems could cause the pilot to need to turn off the master switch and shut down the electrical system.
Now what? Land the aircraft, obviously, but with the emotional pressure of an in-flight emergency and no engine power gauges to reference that will be more challenging than usual.
A simple but effective solution to this potential problem is to simply mark your engine controls. Next time you fly, attach some masking tape to the throttle quadrant, set the throttle to the setting that provides level flight at pattern speed and mark on the tape where the throttle lever is located. Now reduce the throttle to the landing setting and make that mark too.
After landing you can get a paint brush or marker and make a more permanent indication. If your aircraft has plunger style controls, just make a colored ring around the control shaft that lines up with the housing at various useful power settings.
Maybe you could mark the trim control too?
Now, if the unthinkable should happen, at least you will know the engine is set correctly for a safe approach and landing.