to suppress this warning you have to edid business transaction and disable storing results in performance wherehouse. Than you will have only data from last 30 minutes (you can export stream from BT to elastisearch or any other http service that can store those data).
Because of how performance wherehouse database works it's not possible to store as much splittings. This means that your BT has to be changed (for example you can setup smart splitting that will distinguish only top x splittings, rest will be stored in one row.
Keep in mind that often 50K splitting results are too much info to extract a real value from it.Probably you are not going to analyze the trend of all this splits.
A good tip is trying to remove unique values, like for example unique IDs from URLs. Or use the smart spit restrictions https://www.dynatrace.com/support/doc/appmon/application-monitoring/usage-of-business-transactions/splitting-options/
In the worst scenario you could stream it to an external service (elasticsearch is most commonly used), to store all that data.