Macros are defined at the Global Level, Template Level and Host Level and are inherited in the same order.

This allows you to have a macro called MACROX with VALUEX defined globally and that MACROX to have the value over written at the template or host level if is is defined there.

These macros can then be used within such things as template triggers for thresholds and the trigger itself does not have to change and only the macro and value can be changed at the template or host level to provide a different threshold.

I think the same approach would be good for regular expressions that are used in template discoveries for filtering.

You would be able to define a regular expression at the global level @REG_EXP_FILESYSTEM_FILTER to match '.*' which is used in a windows filesystem discovery. For certain templates or hosts that inherit this discovery rule could then have the same regular expression @REG_EXP_FILESYSTEM_FILTER to match 'C:' only.

This way you would not have to update the discovery rule and use inherited regular expressions to change what is discovered based on the template or host etc...