Jonathan Isaac Moss

Thank you for the solution.  It is somewhat strange to need to do the syntax that way but I suppose I understand why it works and at the very least having something that works is all that matters.

If it works it works, even if it isn't as straightforward, I will keep this in mind.

Perhaps I am doing something wrong, but that solution doesn't seem to work.  Maybe this is a separate issue but the "in" dimension execute rule doesn't appear to make entity selection exclusive to that dimension as the purpose from what I understand is to position commands in specific dimensions but it doesn't execute target selectors exclusively in that dimension.

I attempted to execute

/execute in minecraft:the_nether run tag @e[type=creeper] add Nether

and also

/execute in minecraft:the_nether as @e[type=creeper] at @s run tag @s add Nether1

And both of these commands simply execute on creepers spawned in both the Nether and Overworld.  Maybe there is a specific format I'm missing for this?

Oh wow that sounds like a much worse problem than I initially thought if there isn't an alternative way to checking the dimension of an entity, especially now that datapacks are able to add new dimensions and more people will be wanting to do dimension-specific commands.

Also thanks for cleaning up the post formatting.

Can confirm it still exists in snapshot 14w08a. The report should be updated with latest info.