I have some areas like this as well. In my situation, in areas where there are mature beech, most are suffering from beech bark scale disease and are slowly dying. Therefore they are sending up root sprout thickets. Generally I clear them only if making a trail for a mainline or other purpose as they will keep sprouting. In the understory, they won't compete with any maples in the canopy so I don't worry too much about it.

In other areas I have good regeneration from past thinning, and in those areas I may try to encourage the maple saplings by removing other species, especially invasives, but generally I don't do much there either.

I would say that unless they are really in your way, you should leave the saplings there and try to encourage the maples by thinning if they are competing with the beech or others. Generally a good understory is a good thing as it means you have the next generation of trees waiting for a gap to open up. The beech thickets can be problematic though as they may outcompete others species in the near term as they are shade tolerant. Addiitonally, those sprouts will likely never become mature as they will soon die from the nectria fungus.