Hi
A star ground is a specific physical connection form so it has to be forced in the layout editor. Eagle wants to tie things in the same net with the shortest ath - as the flywire flies
When you grab a flywire, you just make a sweeping trace to move the starting point to where you want it to be, then lay the trace, then go back and rip up the sweeping trace. In analogue layouts we have to do this all the time so that grounding and power feeds will be correct instead of how Eagle defaults to shortest path. Remember, Eagle was designed for laying out digital circuits in the 1980s, and that is more forgiving than analogue.
In the schematic, you can stylise it to show that x number of leads tie to a specific ground - maybe there are several stars that need to be separated? Personally, I never use the GND symbol and often begin laying stuff out before the schematic is complete. This lets me control how the connections flow without so many flywires to grab by mistake.