There is a known issue with the BLE 22.214.171.124 and 126.96.36.199 SDKs if a project is created and only a part is specified not a Silicon Labs development board, then when the AppBuilder is run by pressing the "Generate" button the generation action will fail and a "Configuration Error" dialog box will be shown:
The work around is to choose the radio board that has the part with same 'feature set' on it as the starting point for creating the project and then edit the project to remove the board dependencies. The 'feature set' portion of the target part number is the 3 digits after performance grade. For example for the EFR32BG1B232F256GM56, the BG1B232 indicates the Blue Gecko Series 1 family, the B is the 'basic' performance grade and the feature set is the '232'. This url can be used to help select which radio board to specify in Simplicity Studio: https://www.silabs.com/products/development-tools/wireless/wireless-radio-boards#bluetooth The 'BRD' can be used in place of the 'SLWRB' in the part number.