Hi @NiklassonMikaelaDSVas-6096
There is no way around this limit (20000). This may change in the future as indicated on the page below, but I don't believe there is an intention to change it.
https://learn.microsoft.com/en-us/office365/planner/planner-limits
Planner Feedback
You could give this feedback to the Microsoft Planner Team at:
https://feedbackportal.microsoft.com/feedback/forum/a1a93b69-2f1c-ec11-b6e7-0022481f8472
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If this is helpful please accept answer.