Dual boot between Mojave and Ventura

[UEFG]

Hello everybody! Running successfully a 5.1 Mac Pro (2010) with OCLP Ventura. Before updating to 1.4.3 I could easily switch between Mojave and Monterey. The two OS are on separate SSD-drives. Now that I have Ventura and 1.4.3 booting Mojave doesn't work anymore. I can press the drive in Picker but then the computer shuts down and nothing is happening anymore. Is there somebody who could give me some advise? Many thanks for your help!

[UEFG]

Hi again community I tried a few things but didn't make it work.

I found out that when trying to boot the "old" installation of Mojave in Boot picker it doesn't recognise the system (Ø) but when I take out the new system disc (Ventura), booting directly from the old drive works perfectly fine. So it seems to me that the EFI Boot Picker is somehow broken. Is there a way to fix it? Many thanks to you all for reading and helping!

Uli