Are there any links on how to create custom multis, or has this been discussed before?

Actually it's possible I mean custom Combos.

Any suggestions would be helpful.

On Kontakt 5

Sibelius does not allow the mixing of sounds from multiple VDL patches into a single instrument definition. (If it did, the [url=https://www.thewritescore.com/product/sibelius-vdl-template/]Template[/url] would already have some in it - and there would probably be a tutorial on how to create your own.)

Mid-staff instrument changes is the most common way to get different patches on the same staff. A combination of hidden ";play only"; staves and unchecked play-on-pass boxes applied to a visual staff is another way.