<$select tiddler='$:/city-select'>
<option value="">All</option>
<$list filter="[tag[City]]">
<option value="tag[<<currentTiddler>>]"><<currentTiddler>></option>
</$list>
</$select>
<$set name=filterAdd value={{$:/city-select}}>
<<list-links filter:"[tag[Location]$(filterAdd)$]">>
</$set>
<option value="tag[<<currentTiddler>>]"><<currentTiddler>></option>
It seems to me that the main error is the line<option value="tag[<<currentTiddler>>]"><<currentTiddler>></option>
="[tag<currentTiddler>]">
Only single brackets inside the filter. Also when you use {{...}} in filters, i.e then {...}