There are numerous ways to run internal Opus commands. Here's a sample toolbar button definition that will place a "Set Lister Title" button on one of your toolbars. You can use the code below to easily add this button by following the simple instructions in this post describing how to add buttons to toolbars; specifically - the section that describes using XML button defintions.
<?xml version="1.0"?>
<button backcol="none" display="both" label_pos="right" textcol="none">
<label>Set Lister Title</label>
<icon1>#setdefaultlister</icon1>
<function type="normal">
<instruction>Set LISTERTITLE {dlgstring|Set Lister Title}</instruction>
</function>
</button>
The button uses the command Jon referred you to, along with an Opus dialog to prompt you for the title you want to set the current lister to... Once you've done so, go ahead and re-save the layout for that lister and it will now remember the title you set when you reload a lister from the updated layout.
When you're done you can just delete the button from the toolbar, or move it to a sub-menu or someplace most convenient if you expect to re-use it in the future as part of updating your layouts.
Welcome to the wonderful world of Opus 
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