Hello Ayomide and welcome to the Community!
Thanks for coming to the Community to find how to change the date range limit within a Next-Gen roadmap. From your post I can see it’s very similar to another post with an accepted answer. With this said, we ask you to take a look at the following post to see if it helps to resolve your ask: How to extend the Next-Gen Roadmap timeline to beyond end-2021.
Please let us know if the above is helpful.
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