This will do it:
<$list filter="[all[tiddlers]]">
<$checkbox field="selected" checked="true" unchecked="false">
<$link /><br>
</$checkbox>
</$list>
<$button> delete selected tiddlers
<$list filter="[all[tiddlers]selected[true]]">
<$action-deletetiddler $tiddler=<<currentTiddler>> />
</$list>
<$list filter="[all[tiddlers]selected[false]]">
<$action-deletefield $tiddler=<<currentTiddler>> $field="selected" />
</$list>
</$button>
notes:
* the first filter lists all tiddlers, and shows a checkbox for each
* the checkbox adds a field to the listed tiddler: selected=true/false
* the button invokes $action-deletetiddler for each tiddler that has field selected="true"
* the button also invokes $action-deletefield for each tiddler that has field selected="false"
* this is in case you selected a tiddler and then changed your mind and deselected it
-e