I want to migrate PHP settings between computers (from where I have PHPEd to where I've just installed it)

1. Contents of Tools -> Accounts
2. Contents of Tools -> Settings
3. Window/workspace layouts
4. Snippets
5. Keyboard shortcut settings

Basically, EVERYTHING.

It's been long overdue.

for the accounts, there is Export / Import buttons in the UI. So you can easily export / import what you need in the accounts. Exported file is in tar gz format, so you can check what is there actually you're exporting or importing.
As of the Tools->Settings, there is a 3rd party solution that Ian.H wrote rather long ago, but it should work fine -- https://forum.nusphere.com/phped-settings-mgr-import-export-your-settings-t8608.html