Updating multiple Sales Tax tables in gnucash

[J. Anthony Hertzler]

I have a question regarding implementing tax tables for sales tax in 
Gnucash. A year or so ago I asked this mailing list how to set up a tax 
table so that the appropriate taxes on an invoice are automatically 
added to the liability account of each state/city/county where they are 
owed. 
https://lists.gnucash.org/pipermail/gnucash-user/2009-December/032534.html 
With some help I eventually found out how to make that happen, 
https://lists.gnucash.org/pipermail/gnucash-user/2009-December/032590.html 
but as my list of tax tables grows I'm finding that keeping it updated 
is more complex than it seems like it ought to be. Here's what I mean:

We sell portable buildings over an area of fifteen or twenty counties. 
Because we deliver them to the customer, the delivery destination is 
considered to be the point of sale. This means we need a tax table for 
every county that calculates county and state tax, and a tax table for 
every town we deliver to that calculates the town, county, and state 
tax. This might be a total of fifty or more separate tax tables.

Now the state sales tax changes by half a percent. To update my tax 
tables I have to open the tax table editor just before the change kicks 
in, and manually edit the state entry on each of those 50 tables 
individually. This introduces lots of opportunity for error and mistaken 
tax charges as a result.

Obviously this isn't likely to happen often on the state level, but it's 
fairly common for one county or another to change the tax rate, again 
requiring manual changing of each individual town in that county.

Am I overlooking a feature that would allow me to set these tables up in 
a hierarchy such that I could change the state sales tax rate and have 
that reflected in each tax table that included state sales tax? If so, 
how is it done? If not, it seems like it should be considered to add as 
an important feature for businesses that need to make sales in many 
different sales tax jurisdictions.

-Anthony Hertzler