WACK? OK, I'll leave it. Probably not your choice.
Have a look at "Field Series Condition" in your manual.
Yes, it is like an OR as far as the values in series are concerned. Or multiple identical IFs, except with a different value to match.
I've not used it, for the reason you have discovered. Someone looks at the code and just doesn't plain understand it. After a while, you realise it must be an "OR" of some sort, but not convinced until you hit the manual.
Easytrieve doesn't have an equivalent of 88s other than this. 88s is how you'd want to do it in Cobol.
I'd code out the ORs. At least any reader will understand when they see the code. I don't know what would happen if you have, say, three values but you miss the comma out for one of them. You could try, and let us know :-)