In practice if you want to use a railcard for part of a journey, then might need to do it as 2 separate purchases.
Most ticket sites can't cope with changing railcards at a split point in one transaction. You get same problem if you use two together railcards, but one person isn't doing whole journey.
If actually switching railcards, yes (e.g.
@yorksrob travelling from Carlisle to Kent via the S&C and holding Railcards that cover the start and end of the journey

), but this is incredibly niche.
But our site is absolutely fine with combining discounted and non-discounted tickets.
My intention is to buy two separate tickets , I was just wondering about the rail card use. I find it strange I can’t use it right up to the boarder of the covered area just because the train does not stop there.
The whole rail ticketing system/ set up seems very dated and un- paying customer friendly. Me thinks it’s time for a massive overhaul of it
Train companies are very keen for an overhaul that increases the cost of the cheaper fares, so that it is no longer cheaper to split (or to force people to "tap out" and "tap in" again to ensure you need to "step back" a train).
If you have any ideas for a potential new ticketing system, please create a new thread in Speculative Discussion.
However, it is worth noting that the Government is not keen on any new system that would reduce revenue, so if your proposal reduces the cost of longer distance journeys, it is highly unlikely to ever happen.