How to split BSV from BCH that are mixed with coins that have previously been split and are stored on a Trezor?

Thanks in advance to anyone who takes the time to read and comment.

As the title says, I need some help with splitting BSV from BCH that are stored along with BCH that have already been split.

The first issue is that the Trezor contains BCH from which I had already successfully split my BSV some months ago. I then recently transferred more BCH to that same Trezor this past week. The split and unsplit BCH are now effectively held on the same device/wallet but at separate public addresses.

I want to know what the process is to split the BSV from those non-split BCH in the Trezor.

I have read this guide but as I don't have the BCH stored on Electron Cash, and they're mixed with split coins I don't know what the best options are.

Thanks