I've never seen a soap that has actually told the story. EastEnders and Emmerdale had children born into the show with Down's and they have both been on their shows, off and on, for 15-20 years, but they are rarely seen.
Neighbours brought in a young woman with Down's soon before their show ended in 2022. In real life she is a friend of Guy Pearce's so they cast her as his daughter. When the show was revived in 2023 (it's ending again in a few months), they brought her back, and she pops up every once in a while for some light comedy or background moments, not much else.
I just don't think this is a story soaps want to tackle, especially not in such an exploitive time for the genre. They will tell "issue-based storylines," but that tends to be giving 10 different characters cancer or diabetes or infertility or depression.
It would probably take a soap on public television, and that era of public television is long gone.
On paper, this could have been a strong story for Holly, especially when you add in Holly's career, regrets over keeping a baby she hadn't planned, her history of depression (it was implied in 1992 at least, IIRC), but I don't think it was ever going to happen.
The best I can say is the show didn't kill Meg off for awards and misery.