If the splitter just has the typical in and an out, you can run the tractor out to the splitter in and the power beyond to the splitter out. There is some loss of protection in that configuration and you should avoid simultaneous operation of the splitter and 3ph, and avoid lifting more than the splitter with the 3ph. Hopefully the loader is upstream of the power beyond connection so it can provide a relief path and does not add conflict.
If you have a remote valve, you can operate the splitter from that with a bungee on the lever and you will be fully protected.
The other way to be fully protected is to have a power beyond valve configuration on the splitter that uses all 3 connections just like your backhoe. Most splitter valves do not have that feature.