The parameter to a filter operator can be:

hard

[like this]

The parameter is the exact text that appears between the square brackets.

soft

indirect

{like this}

The parameter is the text indicated by the text reference whose name appears between the curly brackets, i.e. a field of a specified tiddler, or the value of a property of a specified data tiddler.

variable

<like this>

The parameter is the current value of the variable whose name appears between the angle brackets. Macro parameters are not supported up to v5.2.0

Introduced in v5.2.0 Literal macro parameters are supported. For example: [<now [UTC]YYYY0MM0DD0hh0mm0ssXXX>].

Introduced in v5.1.23 Filter Steps support multiple parameters which are separated by a , character.

For example: [param1],[param2] or <param1>,{param2}