On the Nuvi 2495 that I have at my desk, you would do "Where To", Then "Saved", "All Saved Places", click on the waypoint you want to delete, then hit the i for information, then the symbol on the top left and then "delete".
I am not sure if it's the same way for your Nuvi 2555, but I hope it's at least very similar.
You cannot delete waypoints from internal memory on your particular device.
You will have to delete the waypoint by using the device itself.
This is a 7 year old thread so I'm not clear what your problem is. All On the road and On the trail devices allow you to delete waypoints on the device itself. BaseCamp can delete data on On the trail devices but not On the road devices, so which 2 devices do you have?
It is a fundamental function of any software that maintains a database to allow the standards of Open Save a file then Add Edit and Delete the data if the operator is authorised to do so. It would appear for reasons unknown that Basecamp does not allow this fundament function of deleting a waypoint or route. As somebody who worked in the IT industry beginning some 60 years ago, that Garmin for reasons unknown do not comply with this requirement. To have to go back to a glass screen to delete a waypoint is out of the dark ages when we used Hollerith Cards to do the same function.
BaseCamp does allow that. However On the road devices do not allow BaseCamp to delete their data. It can however be done on the device itself. The reason BaseCamp cannot delete data on the device is that it's held in internal memory not accessible to the user. BaseCamp can only see it as there is a one way copy of that data placed in the GPX folder on the device named current.gpx
As the way On the road devices work isn't a BaseCamp issue I'm now closing this thread.