https://www.zabbix.com/documentation/2.0/manual/regular_expressions explains how to use a pre-defined regex "everywhere by referring to its name", namely by pre-fixing an @ sign. The yellow box below informs you to enclose it in quotes, if the regex name contains spaces.

Setting up a discovery rule, that doesn't seem to apply as expected:

—

• Define a regular expression called fswin
• Use it in the "Regexp" field

@fswin --> Works
"@fswin" --> Fails

I'd expect that to work, even though there are no spaces.

—

• Define a regular expression called fs win
• Use it in the "Regexp" field
  @fs win --> Works
  "@fs win" --> Fails

That seems to indicate that quotes don't work properly in this field at all, no matter what.

—

Expected behaviour:

From what the documentation says, I'd expect quoted regular expression names to work in this field.

https://www.zabbix.com/documentation/2.0/manual/discovery/low_level_discovery has no example for using a pre-defined regex.