I once added some demos to experience, now I want to remove them from library, but I only find the function of hiding. Is there anyway to remove them just as items in steam?

You may contact GOG support, and request that they remove said demonstration versions from your account. Unfortunately, that is the only option currently available to permanently 'delete' the items.

Yeah a lot of people been asking for a permanent removing feature but they havent implemented it yet.
I have a dozen i'd like to remove from my library, but they keep saying "use the hide feature"

We are all aware of the bloody hide feature! we want to REMOVE them, it puts me off buying games here if i dont have the freedom to get rid of what i dont want, this site is like a tatoo parlour, you buy it you stuck with it.

If they implement an option like "permanent remove this game" but still keep the key associated with your account, it would be completely useless. It's basically the same as just hiding the game.
It means that if you buy the game again, you'll have the exact old key.
Steam does that.

If they implement an option like this, and your GOG account gets compromised by a hacktivist (or other little Gremlin), you could have one or more of your games permanently removed from your account.

Yes, it could be made that such deletions could be reversed. But do you know what's better than making more work for yourself? Not making more work for yourself.

Just hide the title and find a nice rug to sweep it under.

I've never understood the desire for this.
Just use hide if you really feel you have to.

I have hundreds or demos, thousands of games at GOG, and I don't hide any of them.
What truly is the issue? The fact that GOG don't allow you total control?

Shit happens, and GOG already deal with plenty of customers who make mistakes or do foolish things.

Why should they spend time developing a such a feature and when things go wrong, either by the customer or because someone hacked their account etc, spend time fixing things.

It is possible, that even if GOG wiped the game from your library, if you ever decided you want it back, then laws might say GOG have to do so. So why should they support something that could be a headache, when all you need to do is hide what you don't want to see.

GOG already have their work cut out for them. They cannot keep up with things that actually need doing.

A vocal minority keeps clamoring for this feature, but I've yet to see an explanation why it's needed.

For some I would hazard a guess it's sort of like a neat-freak collector thing: the very thought one item in their collection is owned but not wanted claws at some people's minds. Even if it's hidden they "know it's there" and obsess over it. Some sort of compulsion to have their library as perfect as possible.

For me, the games I didn't enjoy serve as a reminder to constantly be more selective with purchases and homepage giveaways. I also appreciate the "In library" tag in the store serving as a warning.

Knowing that it's sitting there, festering in the background; merely hidden and not actually removed, is the one sole reason I don't utilise the demos available on GOG. It's annoying. I have one demo, and this now means there's a discrepancy between the amount of games displayed on my profile (72) and the amount of games logged and displayed in my collection (73). They can't both be right. At least if they were "removed" in the way Steam hides them, order would be restored. Thankfully I'm slovenly enough that knowing Steam still ties them secretly to my account is okay.

I don't get this mentality at all. They even removed the "Search hidden games too" checkbox from the library. To find a hidden game, you have to manually switch the category to Hidden Games or it turns up nothing without explanation.
That's not a problem specific to demos. The correct count is My Collection + Hidden. The profile page is often wrong. You can temporarily fix it by buying DLC. Don't ask me why that works; I've lost track of the post where someone explained what nonsense goes on behind the scenes that causes this.

We should sticky this thread.

It doesn't have to be reasonable, rational, or sensible. It just has to exist.

But I also know that it's stupid to hold this mentality, hence why I don't request GOG to change things simply to adhere to my personally preferences; even if I did take the trouble to state what I dislike, which might have given the wrong impression.