There is, it's even linked in the FAQ actually:
https://www.gog.com/forum/general_beta_gog_galaxy_2.0/suggestion_forum_faq_also_one_sticky_thread_for_each_integration/post13

Just wanna mention that the "windows.zip" is especially for the blizzard launcher, it got other names for other integrations. But it's always that one .zip file in the newest release.

Hello
I see that PS Xbox 360 and PSvita is not support for the moment
In the future did you propose to merge the same game on different store/support
for exemple i have For Honnor on PC PS4 and xbox one I see 3 game en my game list but it's the same ...
it will be interesting to compare archivement on different suport for the same game, not on different pages

You could open a new thread asking for this, we here are just also users helping each other. :) The 'merging' game has been discussed quite a bit... there are other threads you could find. But there are issues either way... first: how do you define the 'primary' store/launcher for the merged game? Then, in other cases, like adding games manually, then you have the reverse problem: you can only add the game once. Anyway, lots of stuff for GOG to think about and implement. I'm sure they are looking around for opinions. :)

A few suggestions for the FAQ... First of all, I don't think creating an account there is as easy as it used to be. Second, to be frankly, I don't trust random gamers to add games properly (with metadata, etc). I've been suggesting instead pople send an 'report issue' reporting the missing games, so GOG itself can add them (at some point) to the database. Do you think that'd be a more reasonable answer? Or people would just try adding the game anyway?

Up to you either way!

If I didn't say before, thank you a lot for doing this! :)

Can anyone answer me about time frame for the 2.0 Beta access? I read how it is done chronologically, and I only just recently applied for beta access. So I am curious as to an estimate of how long it would take to gain access?

I have recently decided that Valve is not worthy of any my gaming dollars (for reasons that would end up as a rant, and very off topic for this post. So I will leave it at that). My aim is to get all the games I purchase from here in from GoG, as both GoG and CDPR are companies I can get behind. Some titles of course are not available on GoG, and alternate means are required to obtain them,. So the ability to have all games over various platforms in one library is one I need and am in full support of. So I am very much looking forward to participating in the Beta! Though it seems that could be far off if there is a lengthy wait list.

No, as there is no linear connection between registration date and granting beta access. But there is this post from a gog staff member:

"No, having no games doesn't affect getting invited. :)
Don't worry, soon everyone will be in. ;)"

three days ago (Source)

Kinda wonder what's the point of integration if we're still require to download and install that "integrated" software?

Well, the vision behind Galaxy 2 is to have one place where everything comes together nicely (in theorie, practically at least now, Galaxy is far from it) especially in an environment with everbody and their grandma creating their own shop/launcher. But as gogs magic wand (for whatever reason) is out of order curently, they just can't wave away the distribution technologies/models other shops decided to use.

Will there be a light theme available soon? The current one is close to impossible to read or use as it makes my eyes hurt after a couple minutes...

If the Liscence to play a game is obtained through steam, then valve as per their Terms of service has the right to force you to use the steam Client in order for the game to work. Gog Cannot strip that right from any company doing such.

In order to remove the need for the third party Clients (Meaning game Clients other than Gog's Galaxy) That company would have to willingly Invest resources into giving Gog an alternative that doesnt require their Client. Hopefully they figure out a way and are willing to do so but It's not likely.

The best solution Gog can offer on its own Is a function In Galaxy, which closes those third party clients as soon as you exit your game. Which does solve some if the compatibility issues related to running multiple game Clients.

It's not an Ideal solution but atleast its something to have in place while we wait to see if Valve and others are willing to actively support the Galaxy Client.

Has the latest version of Galaxy 2.0 brought back command line arguments for games (Quake, etc.) yet?

Sadly no.

I hope it will substitute some clients. Really hate how much useless software junk like Steam I need to install just to play one game.

So far no problems with 2.0. Nothing that relaunching the program couldn't solve.