{ "awesome": [1,2,3,4]}<$list filter="[list{MyData##awesome}]">
</$list><$list filter="[title[MyDataTiddler]indexes[]]"><$list filter="[title[MyDataTiddler]getindex{!!title}]">You're a tiddlytext magician. I never thought about your first suggestion. That is what I was trying to do, it is not a problem to convert the field to a list in TW format.
I was almost happy with my previous solution, but I feel that now I have to rethink it.
Thank you very much