Following cleverraptor's guide I am trying to merge 'Ancient Dragon Lightning Overhaul' with 'Syyyke's All in One 2.5' (using the .csv files provided by Ancient Dragon Lightning Overhaul), but for some reason instead of just adding the new rows or overwriting specific rows it completely replaces all of them. For example, instead of only replacing "[Incantation] Ancient Dragons' Lightning Strike" under the Magic param like it should, it reverts all of the edits made by All in One 2.5 and only leaves "[Incantation] Ancient Dragons' Lightning Strike" edited. It does this with all of the other params too, not just Magic. Is there something I'm missing or am I just stupid (or both)?
#merging mods reverts edits?
leaden marsh
round coral
sounds like the author just dumped everything to csv instead of modifications.
I feel like I'm beating a dead horse every time I say to stop uploading csvs 
In any case, download the mod itself, search 'modified' in each param, select those and export the changes yourself.