Is your feature request related to a problem? Please describe.
Related to the Occultism changes where pentacles don't show if advancements don't unlock properly

Describe the solution you'd like
I'd propose a simple change to modonomicon, perhaps in the client config, that allows the Unlock All button to ignore advancements. Some players simply want to unlock the book and be able to look at things freely.

A condition type that check a setting is very interesting

patchouli has this, there is a client side config to unlock all books to ignore advancement based progression... would be very good for modonomicon to have similar!

For players:

As a workaround you could always create a creative world and unlock all advancements via command

For impl:

AdvancementConditions could always just return test(): true when a config value is set. But that leaves all other unlock conditions, which is probably the main intention of the request here.

For modders:

If that was implemented, I'd like a flag to force that setting to not work for specific books (in the book.json?), which would make this config setting a bit moot again. Some mods are very progression gated and unlocking everything all at once without having all the necessary requirements would lead to chaos and confusion on the players side.

For players:
As a workaround you could always create a creative world and unlock all advancements via command

As a player, I'd much rather have access to the pentacles in my play world than to have to swap back and forth until they're finally unlocked. One of the first things I do to Patchouli is to toggle the advancement blocking off so I can see the book and browse it as I wish.

From a pack dev side, it's also nice to not have to fully re-write a mod's book just so we can change up the progression steps in an Expert pack. An allow/deny list would also be suitable (and is what Patchouli implements as well as a simple toggle).

Ultimately, a change like this is about options. The more the merrier.

From a pack dev side, it's also nice to not have to fully re-write a mod's book just so we can change up the progression steps in an Expert pack

o.O

While I am not a pack maker, but a modder, isn't guiding the player across a customized progression path not the main selling poing of the whole pack, when creating an expert pack?

Just unlocking everything and let the player figure stuff out will inexplicability make the player fail to grasp how progression is laid out without having to study the whole book, since the progression path changes are only partly reflected.

While this is seemingly a 'quick win' for the modpack authors side, it will put the burden to figure everything out on the shoulders of the player instead.

That's what quests are for.