I need some help making some synth presets, hopefully using free synths like Surge, Odin, Zebralette and Dexed, but open to whatever. Anyone good at this stuff? I just don't understand synths at all

For one of my bands, I end up playing keyboard on guitar using a Mooer E7 pedal, but now I'm trying to do this with plugins instead using Jam Origin MIDI guitar to generate the MIDI data.

I need to make one of these plugins sound like Dio's Rainbow in the Dark and Last in Line

I don't think there's any need to go to the trouble of making one. It might be a good idea to listen to all the presets for each VST when you have time.
You can get a feel for the atmosphere by inputting notes in MIDI, playing them on a loop, and switching between presets.It's not about how you create a preset, it's about choosing a preset. You might find a preset that's better and more suitable for you than the one you had in mind. It might be a good idea to search for presets by tone genre.

Last in Line sounds like a brass sound with several stacked synths. Layering synths is done by copying the same melody to two or more lanes and applying different presets. This gives you a thick, elaborate synth sound.
Rainbow in the Dark might be a good choice if you're looking for something in the brass genre.
If you choose well, you may end up with a sound that sounds better than you ever imagined.

If you're not good at making things, try looking for something similar.
For tracks of instruments other than synthesizers, I find it easier to find a matching preset if you keep the track playing.

Dexed has something like 3000 presets in the download. I found a few curated ones that come sort of close, but not really sure which to use or to layer. I really need the attack times different on most of them but its not always straightforward on how.

I saw a korg video showing rainbow in the dark, I wonder if their own keyboard plugin would do this



This one would be great for last in line!