ZDoom

Ah, I see. That's disappointing, but it makes sense. Although it worries me a little bit that the other use cases I had in mind may be less similar than I had hoped, and may require yet more distinct solutions...

This cannot be done after initialization. IWASDINFO is read before the resource directory is created so that the tagged lumps get deleted right on creation. Deleting data later can cause problems because you have no way of knowing if that data is already in use.

For the specific use case something different is needed, this cannot be safely handled with a lump deletion mechanism.

I'm not sure I understand any of that. But, I was envisioning something along the lines of making the DeleteLumps command accessible outside of just iwadinfo, perhaps in conjunction with the recent discussion of allowing substitution of specific lumps/strings in mods: https://forum.zdoom.org/viewtopic.php?f=49&t=63737&start=465#p1118542

Turning GZDoom into a wad editor would be a hell of a huge feature creep.

Best to use [url=http://slade.mancubus.net/]Slade[/url] for that.

Once in a while, a mod that used to work with GZDoom will break because the engine's error handling/checking became more robust with time. Unfortunately, sometimes this is something that cannot be patched over in the mod with a second add-on file. An example would be Doom Resurrection (https://www.doomworld.com/idgames/levels/doom2/Ports/d-f/doomres), which no longer works because an erroneous S_END lump causing confusion/conflict in the namespaces prevents the mod from launching. Currently, there is nothing a patch can do to fix this. However, if the ability to retroactively delete a lump was possible, maybe a patch could be created?