Recently to have the map contact identifiers and map contact identifiers source checkboxes selected by default.
My intitial thought was to go into the core database and look for a setting to update but I was only able to find ways to add default and custom facet properties to the wizard. I then found the application located in \sitecore\shell\client\Applications\ListManager and started looking at the ImportWizard.js. Fortunately, I was led to the correct file by Artsem Prashkovich. It turns out I did not dig deep enough and the file in question was the ImportmapTo.js located in the following folder: sitecore\shell\client\Applications\ListManager\Controls\ImportMapTo
Not only did I have to make the changes suggested but I also had to remove hide() and Off() methods which are highlighted below.
After clearing the browser cache, things worked as expected.
NOTE: These files should not be directly edited. You can lose your changes or experience other issues when doing upgrades. I hope someone finds this tidbit useful.
15+ year programming professional with 10+ years devoted to Sitecore development. I've been using the platform since Sitecore 6.0 and currently serve as a Technical Architect at Verndale.