wa never used, da forgotten, en not needed.
(30.11.2017, LyX 2.3.0 release )
Additionally to the top ones, these languages should be reviewed for the following strings
"List of Listings"
-ar bg ca da el en es eu fi gl he hu ia id ko nb nl nn pl pt_BR ro sl sr sv tr uk zh_CN zh_TW
+ar bg ca da el eu es fi gl he hu ia id ko nb nl nn pl pt_BR ro sl sr sv tr uk zh_CN zh_TW
"Nomenclature[[output]]" -> The string that is output to PDF for the nomenclature list
"see equation[[nomencl]]"
"page[[nomencl]]"
-ar bg ca el eu fi gl he hu ia id ja ko nb nl nn pl ro sl sr sv tr wa zh_CN zh_TW
+ar bg ca da el eu fi gl he hu ia id ja ko nb nl nn pl ro sl sr sv tr zh_CN zh_TW