If you're not married to XMediaRecode but want to use a GUI, try MeGUI. You can just add the timecodes file in the x264 encoder configuration.
https://i.ibb.co/QvhkcMG/1.png
I still don't know if x265 has a VFR mode and MeGUI's x265 encoder configuration is pretty basic anyway.
I'm not sure I understand the "linear access" problem you mentioned earlier, but the TIVTC plugin has a RequestLinear() function if that's any help.