You can get the best of both worlds; Categorize by popup value and automatically add to Category check-mark folders  
 
1. Create your Category folders as check-mark folders
 
2. Create a Popup Folder with the same Categories.
 
3. Create a text file "luacmd.lua" in the Ecco program directory.
 
4. Add the function/Script as shown below to "luacmd.lua" files and save (The
Script lists examples of Categories - modify as desired).
 
5. In any folder (I have a check-mark folder called "LUA Scripts"), create the
following rule:
 
++:L:SetCategoryFolder(item_id)
 
6. How it works:
A. When you set the popup value, the corresponding check-mark folder will be
checked.
 
B. Changing the popup value changes the check-mark Folder.
 
C. Note that the reverse is not working, i.e. it is not possible to change the
check-mark folder to change the popup value. This can be done but it is a bit
complicated.
 
D. Thus, trying to change the check-mark Folders is prevented. It will simply
revert back according to the value set in the popup folder.
 
E. If a new item is created w/o a popup category value, the popup will get the
value "Unassigned" and the Unassigned check-mark folder will be checked.
 
F. Note that only one category/item is permitted (because only one popup value
can be set)
 
 
 
====== Script to add to luacmd.lua =======
 
function SetCategoryFolder(item_id)
tCategories={"Car","Computer","Duty","Education","Family","Finance","Fun",
"Health","Home","Investment","JobSearch","JobDo","Legal","Tax","Make$",
"Other","UnAssigned"}
Category=get_folder_value("Category", item_id)
if Category~="" then
for index,TestCategory in ipairs(tCategories) do
CurrCategory=get_folder_value("Category", item_id)
if CurrCategory==TestCategory then
set_folder_value(CurrCategory,item_id,1)
else
set_folder_value(TestCategory,item_id,0)
end
end
else
set_folder_value("UnAssigned",item_id,1)
set_folder_value("Category",item_id,"UnAssigned")
end