Advice needed for best procedure to make large changes to keyword hierarchy

[Curtis]

I've been trialing iMatch for a week now working with about 10,000 photos. They have hierarchical keywords out of Lightroom which were read into the iMatch database quite well. I imported those keywords into the Thesaurus successfully. I want to do extensive restructuring of my keyboard hierarchy which again is already applied to the 10,000 photos in my collection. I'm confused by what I'm reading about how to do that correctly. 
(1) Should I make the structural changes in the Thesaurus and write those back to the Database using the icon at the top of the Thesaurus? I see warnings to make a few changes at a time so as not to create side effects. I have encountered lost tags using this method. Most of the retagging works, but some keywords end up with 0 keyword counts in the @keywords list in Categories. It is here that I have problems with the updated structure carrying over. The Keywords panel updates with not problem.
Or (2) should I make my hierarchy changes (spellings and changes in levels) in the @Keywoards section, which I like because I can do it easily with drag and drop and can see and check the character counts in the old and updated structure easily, and then use the Import from Database option in the Thesaurus to make the Thesaurus and Keyword list congruent to the @Keywords structure?
Is it a matter of preference or is one more definitely the correct method for what I'm trying to do? Thanks in advance.

[Mario]

The @Keywords category basically reflects the actual keywords in your files. It automatically updates whenever you change keywords in some way. It offer some extra features, like quickly renaming or moving keywords.
See The @Keywords Category for detailed information.

Note that changing keywords in files via the Keywords Panel or the @Keywords category does not change the contents of your thesaurus. The thesaurus stores the controlled vocabulary for keywords and should never been changed implicitly.

You can apply changes to your keywords globally by enabling then corresponding option in the Thesaurus Manager. Changing keywords that way will change the keywords stored for your files in the database and this will also change @Keywords.

@keywords list in Categories. It is here that I have problems with the updated structure carrying over.

We would need more details on this. Keywords before, changed how, what is the actual problem caused by this etc.

It is quite easy to shot yourself in the foot by using advanced features like global keyword changes via the thesaurus after using IMatch only for one week.