So I hope I understood the question, but it’s around the finding / populating of the list, not the transcluding bit… If that’s right, it sounds like what I do for marking down who attends the meetings I’m in for notes purposes. Like the below where I expand an area out for a search-box that shows the first 10 contact matches, and with a button, adds them to a list field.

Here it is raw - plenty to strip out that do more than you need.
Attendees:
<$list filter="[all[current]enlist{!!attendees}]" variable="attendee">
<$link to=<<attendee>> tooltip={{{ [<attendee>get[jobtitle]] }}}><<attendee>></$link>
<$button class="tc-btn-invisible tc-tiddlylink">✖<$action-listops $field="attendees" $subfilter="-[<attendee>]"/></$button>,
</$list>
<$list filter="[{$:/temp/add-attendees!!meeting}!match<currentTiddler>]" variable="x">
<$button class="tc-btn-invisible tc-tiddlylink">▶<$action-setfield $tiddler="$:/temp/add-attendees" $field="meeting" $value=<<currentTiddler>>/></$button>
</$list>
<$list filter="[{$:/temp/add-attendees!!meeting}match<currentTiddler>]" variable="x">
<$button class="tc-btn-invisible tc-tiddlylink">◀<$action-deletetiddler $tiddler="$:/temp/add-attendees" /></$button><br>
Add: <$edit-text tiddler="$:/temp/add-attendees" tag="input" size="20" default="" focus="true"/>
<$list filter="[{$:/temp/add-attendees}minlength[2]]" variable="x">
<$list filter="[tag[Contacts]search:title{$:/temp/add-attendees}first[10]]" variable="contact">
<$link to=<<contact>>/>
<$button class="tc-btn-invisible tc-tiddlylink">✚<$action-listops $field="attendees" $subfilter="[<contact>]"/><$action-setfield $tiddler="$:/temp/add-attendees" $value=""/></$button>,
</$list>
</$list>
</$list>
Some things I’ll eventually get around to adding would be:
- A way to re-focus the edit-text after adding
- Keyboard shortcut to add the first returned result
Hope that’s helpful,