I've set some sizes in the whitelist and was testing it out. I noticed something that I wasn't expecting. I'm not reporting it as a bug because I'm not sure it isn't by design, although I think it's more likely just an oversight.

If I set a whitelist entry of 2xN, then I can merge chests in rectangles that are two-wide and any number of chests tall, but not two-tall and any number wide.

The simple workaround is to also add Nx2 as a whitelist entry, but I would have expected entries using the wildcard in one dimension to work either way without requiring the separate entry.

It is intended behaviour to not mirror whitelisted chest sizes. To allow finer mod setting.

But you are second one who was confused by this so maybe it would make sense to allow mirroring.

Maybe just clarify in the tooltip? The only reason it's irritating is that once you realize it you have to restart the app to change the setting. If the setting hint made it clear from the outset, it would be a non-issue because there's a simple way to configure it as you want.