Literal filter parameters can be used, but such cases are better rewritten without using subfilter:

The subfilter operator can be used to dynamically define parts of a filter run. This is useful for sharing a common pieces of a filter across multiple filters.

For example, this variable:

• recent-mods: [has[modified]!sort[modified]limit[5]]

can be used in one filter like this:

and in another similar filter like this:

Variables are not the only way to define dynamic subfilters. Text references can be used to load a subfilter from a tiddler field (see also Filter Parameter):