You would also need to add the svd file to a new folder in the platform, called misc/svd, like e.g. in ststm32.
Also for the debug interface with Raspberry Pi’s GPIO pins, the config files are described here. And for the picoprobe it would need the interface/ picoprobe.cfg file. But attention: This is again in a different branch in the openocd repo, picoprobe. Seems confusing to me that there’s a a rp2040 branch (which doesn’t have the picoprobe file), a picoprobe branch and a rp2040_jlink branch, each featuring something different…