Multi-level TAG selection in FIND/REPLACE?

I have a category with a slew of subcategories starting under 
"HOUSEHOLD" (children would be items such as MAINTENANCE, FURNISHINGS, 
UTILITIES, etc").  I rented an apartment for a few years, so I've tagged 
those as "CINCINNATI" so they can be listed separately in a transaction 
report under the HOUSEHOLD expense category.

Now, I am moving and my default blank tab I'd like to have as my new 
location.  Thus, I'd like is to do a massive FIND/REPLACE for the 
category and children under "HOUSEHOLD" with ONLY those tags that are 
currently blank.  That way I can then tag them with "OLDHOUSE" so the 
untagged ones created in the future are the new house and the 
"CINCINNATI" tags remain.

I can't find a way to do this. Is it possible?
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Regards -

- Andrew