Installing ductless units in my apartment. What am I supposed to do with all these coolant and drain lines?
The condenser lines are most likely loops.  Each air handler (inside device) has a refrigerant loop to circulate fluid out to the exterior condenser/chiller.  If you are thinking of combining them into a common conduit of some kind, or simply covering them (like surface-mount electrical work) as they run on the walls, I think that's fine as long as the conduit/covering doesn't hold water in.
The drain lines are another matter.  It's easy to connect them together into a common line.  You can also direct that water into a plumbing drain.  It doesn't necessarily have to go outside.
Take care to plan the drain path so they have enough slope to avoid collecting water inside them long-term.  1/4&quot; slope per foot of drain line is a good amount.  If there are low spots in the line, those can clog up with organic growth such as mold or fungus, and then the AC unit ends up dripping water instead of draining correctly.
Condensate pumps are very small pumps commonly used if you need your AC drain line to go up, for example, if it's easier to route the line through an attic than under a floor; or if you need a way to get the water back up from a basement.
Hope this helps.