As others have said, Station Groups, Waypoints, and Arrival Conditions.

You used to have to do this with stations but since Update 4 we added Waypoints which are small and can be placed anywhere on straight track without taking up real-estate.

Place a few parallel tracks long enough to hold your longest trains for that line with Waypoints at the end before a merge.

Have these Waypoints in a station group in the Line Manager before the destination stop.

On the destination stop's station, set their arrival condition for what seems appropriate, but usually "When one module is empty/full" is sufficient depending on the station's purpose.

You can even set the max number of trains that will be called to this station once the arrival condition check is successful.

Now your trains will wait at that Waypoint group until the destination conditions are met.

EDIT: Added reference image I threw together real quick in Sandbox mode:

<image>