Hi Gary,
Yes, we can increase the lookup field item limit from QuickApps for SharePoint Configuration Editor, by default it is 2000.
Please follow the following steps:-
1) Open QuickApps for SharePoint Configuration Editor.
2) Select your Web Application.
3) Click on Edit Custom Setting button.
4) Click on Rollup and Query tab.
5) Edit Max Query Row Count.
Thanks
Deepak Tyagi