Matybe I wasn't clear enough....
I can get input into a field ("search") and assign it to a variable eg.
\define thisList()
<$list filter="[tag[$(TestVariable)$]]">
\end
<$set name=TestVariable value={{!!search}}>
TestVariable is <<TestVariable>>
This list is <<thisList>>
<br>
</$set>
<$edit-text field="search" default="" placeholder="enter text to search"
tag="input"/>
<br>
this will list all tiddlers tagged with the value of the field "search"
but I can't work out how to use that search term in another existing macro as a filter such as....
<<timeline-vertical filter:"[tag[search]sort[date]]" date:"date">>
or
<<timeline-vertical filter:"[tag[search] sort[date]]" search:"$(search)$" date:"date">>
any ideas please?