First, before others remind you that sharing software is illegal, I’ll mention that Montserrat is licensed under an open font license that allows for unrestricted redistribution.
Second, all you can do is collect the font files and place them in a folder — either manually or along the lines that PrintDriver suggested.
That won’t solve the problem I think you’re getting at about controlling the order and organization in which they’re displayed, but really, it’s all you can do. If I understand your question correctly, there’s no way you can organize them and have that organization carry over and be used by another program or operating system.
The organization, listing, and collation of fonts within font families, or whatever one wants to call, it is determined by a combination of how the designer named the individual fonts and the software being used to displaying the list of those fonts. Font Book handles it one way. Adobe handles it another. Microsoft has their own way of doing it. And different versions of different software often handle it differently from the versions that came before or will come after. There are no industry standards governing this, and it’s nothing the end user can control.
In the example you posted, you also have a combination of OpenType and TrueType fonts listing themselves as being in separate families, even though they’re really not. Again, though, you can’t do anything about this short of converting one to the other with a font editing application, and doing that can often create other problems. Maybe you could head back to Google Fonts and download them again to see if they’re all available as either OpenType or TrueType.
As sort of a side thing, I design typefaces and build fonts. All the workarounds and hacks that go into getting the individual fonts in the right order for this application or that operating system is something of a nightmare. It should be simple, but the lack of standards prevents that.