Maybe codetoolsoptions.xml ?
I haven't checked though.
I don't know from the top of my head what goes into which of the xml files.
But as I said, if you backup before making changes, then a (folder-) diff will give you the answer.
Lazarus does not store anything in the registry (innosetup does, but that is only for the unistaller)
There are more xml file in the PCP. (And it Lazarus 2.3 there now also is debuggeroptions.xml).
And the settings should be in those xml files.
The one xml file you do not wont to copy: packagefiles.xml
Because it's just paths.
You can put it in a backup, if you restore all installed packages too (and to the exact same location).
But a new install, you probably install the packages from scratch, and then packagefiles.xml will be an annoyance.
If you have your own code templates, they are in lazarus.dci
The other NON-XML files are likely better not copied to new installs.