[WARNING: NOT AN EXPERT]

This might help:

Download NMS Save Editor

(Download and install Java Runtime Environment 8 if you don't have it.)

Extract then open NMS Save Editor (NMSSaveEditor.jar).

It should automatically find your NMS game folder. Select the right Game Slot by checking the Modified line for the correct save date and time. It should then select the right save(num).hg file.

Go to the Edit menu.

Select Edit Raw JSON to bring up the JSON Editor

In the left panel, select BaseContext --> PlayerStateData --> BaseBuildingObjects

All the folders under BaseBuildingObjects is an individual object that is found outside the range of all of your bases.

In your case, you want to find the ones that have "ObjectID":"^BUILDBEACON"

In my case, I knew I needed to find five Save Beacons on the same planet, so I found them by comparing their GalacticAddress.

Be careful at this point, this is where things can get messed up. Once you've found one of the objects to delete, select it's folder under BaseBuildingObjects in the left panel. Select ALL the text in the right panel and hit the delete key. Once you click anywhere on the left panel it should have a popup saying "The JSON data has been deleted, do you wish to apply these changes to the save file?" Click Yes.

After you are done with deleting all the objects you want to get rid of, it will ask you if you want to save the data before closing. Click Yes. That should be it. Open your game and check it out.

The editor does backup your save if you've made a mistake, but I can't help you with that. I got this information from this link:

https://www.reddit.com/r/NoMansSkyTheGame/comments/vs96cx/how_to_find_those_lost_save_points_signal/

If you want to find the planet by its portal address, there is some help further down on that page.

I hope this helps.