Hi @smorele
Good to know that you are asking for how to know more about Odoo internals.
You need to find what is what you are looking for, in your case it's not a variable, it's a group name declared in an xml file as:
<record model="res.groups" id="group_partner_manager">
<field name="name">Contact Creation</field>
</record>
Defined on addons/base/res/res_security.xml file, so basically you will find the usage in the source code files and have often to search for .xml, .py, and .js files to get the usage of a variable or a behavior, .js files will be the last resource but there are stuffs that you will only found there. There are other files extensions on Odoo but normally will not give you results of variable usage like: .po for translations, .rml old report format, .css styles, and I could figure out any other relevant.
After you get more familiar with Odoo you will learn how to find where you will get more chances to get a good search result. but always try to filter the results to only one file extension because if not you will get to much usage and will be a mess to follow the thread. Normally you apply a search on the addons/ folder but that will exclude Odoo core files like models and fields and it will be ok to search for modules fields and methods examples or code usage
Hope this help you a little