I recently migrated to GoG because Steam sucks so badly. They did have a relatively easy string of folders to find the Witcher game foldeers and add the Mods folder. I have looked at all the GoG folders under x86 Programs and I see bin and recognize the game save file, but unlike Steam there is no common file with various game files. Where is the Witcher 3 main file on GoG? Please give me the folder string starting under x86 Programs. If this has already been addressed I can't find it in here and I have limited patience with constant searching of hundreds of threads. Thanks in advance.

Stop saying "file" when you mean 'folder'. A file is a program or a piece of data for a program.
witcher3.exe is a 'file'.

A folder is a container for files.
C:\Program Files (x86)\Steam\steamapps\common\ is a 'folder', NOT a file.
C:\Users\<USERNAME>\Documents\The Witcher 3\ is a 'folder', NOT a file.

Now to your problem. It will be easier if I refer you to a youtube video explaining how it's done. This is for Steam, but GOG is the same. You just need to find your installation folder.
https://www.youtube.com/watch?v=zGXskcB8Li4

Had the same problem myself. The guides online weren't clear and failed to understand the problem. Rather than trying to manually install the kids, use the Mods manager from Nexusmods. It'll get the mods right where it needs to be.

It has been 2 years so I guess it has been solved.