How to get Category 1 Values in selection screen?

Hi All

Good day

I had a custom report where i need to show in selection screen with category 1 values with drop down.

how can i get those category 1 values which are visible in webui incident page in report selection screen?

As per my requirement Currently i having 6 values in webui under Category 1 ,in feature they may assign some more values through category schema

how can i show dynamically if they add some more values in feature in the selection screen of custom report?

Please suggest your comments to get Category 1 values from which tables i can get those 6 values to display in report selection screen?

please find attached screen shot where category 1 having 6 values.

Thanks

Shaik