First, I'm not sure we're on the same page, so let me reiterate and slightly expand on my previous posts. The LTEX is not a true record. It is either "new" or "base" (a limitation of the save format). You can not modify a base LTEX for several reasons. One, it simply does not make sense. The "base" LTEX records are the LTEX records for different plugins, not the current plugin. Any such changes would not persist between sessions. It would show up as a "new" record on reload. Two, under the hood we would need to modify every single LAND that references it. I'm fairly certain this would be bad for multiple mods. Any mod changing a base LTEX would conflict with others that modify LAND records. I haven't been able to test it, but from what I've seen in the source code it looks like the last one loaded is picked. We should try to avoid having such a tool where the consequences (significant mod conflicts in this case) are major and not made obvious by the gui. I would suggest having an "import" tool instead that will mark as modified all LAND records referencing a specified base LTEX for the use case where a user wishes to change an LTEX across all LAND records.
So to clarify my previous post, there are two LTEX records. The base LTEX and the added LTEX. After changing either the user friendly name or the texture referenced by the LTEX record, we cannot know that the base and added LTEX are referencing the same thing. Thus when modifying a base LAND, another LTEX will have to be added.