I'd like to know where to find this info, too!

I figured this out after digging through their dll files (JetBrains FTW!). All the strings are found in: [steam_install_location]\SteamApps\common\War For The Overworld\WFTOGame_Data\Translation\GameText.csv

I recommend using a text editor that can search for multiple strings in a document (ie. notepad++) since the file is 15,000 lines long...

The first parameter on each line is the string key to play the VO. What is said can be seen a few commas over from that. Not all the lines are VO strings, but for other parts of the game (ie. ui, mouseover info, etc). Generally if it has alert_, it is a VO, but some other VOs work differently like campaigns or tutorial VOs.

ie.
alert_artefact_makehappy_discovered,,4,,D,Y,Y,E,,Y,,,You've discovered an Artefact of Joy.,You've discovered an Artefact of Joy.,,You've discovered an Artefact of Joy.,Vous avez découvert un artefact Joie.,Hai scoperto un artefatto della Gioia.,Du hast ein Freudenartefakt entdeckt.,Has descubierto un artefacto de hacer feliz.,Вы нашли артефакт «Счастье».,Udało ci się odkryć artefakt

alert_artefact_makehappy_discovered = string you put in the play vo action
You've discovered an Artefact of Joy = what is said by Richard/Narrator and what displays (for whatever language is selected) in the subtitle box on the screen

Note: If searching for a specific string, Defense is spelled Defence in this file. Proper English I guess? Also Artefact vs. Artifact.

PS: What is a Pighibitor!? (I played it, it is a VO saying "Pighibitor completed!")

I made a small map to test out some vfx and VOs. You can download it if you need to see how it works. VOs will play in the order they are activated, so if you play 10 VOs, they won't all go off at the same time but will enter an audio queue and play one after the other. I think the time setting in the play VO action is the minimum time to allow to say a VO and if a VO is longer than that, it is ignored, but if it is less, then it waits that long before playing another VO.

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1375644195

In this map I play a VO to tell the player to build a defense, then I spam "A minion has entered your dungeon", then I add "Well Done Overlord" when the objective is completed.

Thanks a lot for digging this up! Maps feel much more "complete" with narration