Apple - Where are Google Chrome bookmarks stored in macOS for multiple profiles?

As you've stated, the default location is found within:

Users/<username>/Library/Application Support/Google/Chrome/Default

However, when you create additional profiles, the name Chrome uses on the associated profile folder is a generic numbered name (e.g. Profile 2, Profile 3 and so on)

The best way to find the folder path for a particular user is to:

1. Within Chrome switch to the other profile
2. Chrome will open a new window using the profile you just selected
3. Now in the URL/address bar enter the following: chrome://version
4. Press Enter
5. The browser window will now provide a whole range of data
6. Look for the Profile Path entry
7. This will show you the exact file path location of the profile you selected at Step 1
8. Now you can use that path to find all the data associated with that profile

Additional Chrome profiles are stored in:

~/Library/Application Support/Google/Chrome/Profile 1, ~/Library/Application Support/Google/Chrome/Profile 2, etc...

along with their corresponding bookmarks file.