Resolved in: WPML 4.3.5 and ST 3.0.5
Due to an issue in older WPML versions, you could not translate Toolset Layouts in WPML Translation Management. This would happen even if you could select the Type “Layout” in the “filter by” dropdown menu because you would still not have found any available translation.
Due to this, some WPML/Layouts users started to translate the contents using String Translation, because there, the contents were mistakenly made available for translation.
With WPML 4.3.x those strings were removed from WPML String Translation. However, in the above-described cases, Layouts should have been translated using WPML Translation Management but were not. Because of this, now their translations don’t appear as translatable in WPML String Translation and are not translated in WPML Translation Management.
You should translate the Toolset Layouts strings ONLY in WPML Translation Management.