According to ZBXNEXT-1286 values used in triggers, created from custom user macros by lld, are supported only in numeric form.
Please add also support for strings.

I want to create custom discovery script, that is returning data like:

{
    "data": [
        {
            "{#FSNAME}": "C:",
            "{#FSTYPE}": "NTFS",
            "{#FSWARN}": "{$FS_C_WARN}",
        }
    ]
}

where values in "{#FSWARN}" are created dynamically based on drive letter (by script).
Then I want to make trigger protetypes:

{IIS01:vfs.fs.size[{#FSNAME},pfree].last()}<{#FSWARN}

to get triggers looking like that:

{IIS01:vfs.fs.size[C:,pfree].last()}<{$FS_C_WARN}

My problem is that we have a lot of windows servers with different drives letters, and alerts thresholds. For now I manually add templates with correct drives letters and thresholds, but it will be really nice to discover all disks and only set correct values for macros.