Greets!
Example setup:

Goal:
- Default Company and Department from Requesting Location record -- this works with the above setup (values blank at Account Group; populated on the Requesting Location record)
- Default Account from Item record -- this does not work because we have the 62100 value here
The Account Group requires some sort of value to be selected (i.e., the whole Issues section cannot be blank -- which ideally is exactly what we want to do here and have it default from other places). We currently do not use Service Lines, so the thought of creating a dummy account came to mind, but we also do not want to "muddy" the data more if we do not have to.
We did find this section which will allow us to change the priority to the Item record:


However, this does nothing for manual Inventory Transaction Issues, which would still default to the 62100 value from the Inventory Location Account Group record. (Side note: we also learned that the account setup on the Reason Code overrides the account setup on the Inventory Location Account Group, which makes us lean to no longer using reason codes with our setup).
If we are unable to bypass this defaulting from the Inventory Location Account Group, then the only course we see is to create a unique Account Group for each applicable Account within an Inventory Location (e.g., 62100, 62107, 62108, etc.) and assign the appropriate value to each item within an Item/Inventory Location record (old IC12).
Since this value already exists at the Item record level (old IC11 Issue Account), we would rather just default from there if possible.
Thank you to anyone who might know more around this topic. We are learning what we can throughout this process.