when I tried to amend the 'tool' information to 'project' it unghosted/highlighted the SAVE option, but when I saved it, and went back to it, it had failed to save the changes

Are you sure the icon for the edited file really existed? If no, it is obvious that any changes cannot be saved.

or just copy another icon that you wanted it to inherit with the copy command via the CLI/Shell

It still works.

every damn time you open a window you have to go through the 3 stage process of 'showing all files', then show 'thumbnails' then you have to open the menu again to snapshot all in that window, or the next time you look through that folder you won't see what you want to be able to see straight away

No. Just make sure the drawer you are snapshotting has a real icon. Shapshot settings are stored in icon, the same as in AmigaOS 3.9.

OK, that works, but what a laborious method of being able to do that.

I guess changing the icon image with drag&drop is less laborous than launching an icon editor and loading image into it.

What happened to the efficiency of the OS to put the user in a situation where they are not able to automatically make visible ANY, and ALL icons/files, even if they are default icons, and even if they do or do not have an icon for pity's sake.

There are cycle gadgets in each ambient window for fast switching between icon/list view and between showing all files or icons only. It can be also snapshotted for any drawer having an icon + it can be set globally for non-snapshotted window.