How to modify location names on the map?

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Are there any guides or solutions about how to modify toponyms on the map? Yes, there is edsub.pdf but it outdated or unformative. I tried to correct some names and add new but its so confused.

It's done through the map editors.

Yes, through the submap editor. There is the manual for it also. But the issue is that edsub.pdf isn't informative despite that submap editor looks simple. E.g. you can accidentally make mouse click on the map and it erases a location name somewhere around. 

Correct. That is a good point. When you right-click it will delete the nearest label. So it is important to click on the correct label. This should be mentioned in the submap manual, as it is an easy mistake to make. Thanks.