Hi Gerriko IoT,
Two default packages come along with Modus1.1. One is 'PSoC6 SDK' and other one is 'BT 20819A1 SDK'. If you want to upgrade the application package of 20819, please uninstall 'BT 20819A1 SDK' and install 'BT SDK1.3' (latest package for 20819) from ModusToolbox BT SDK 1.3 . (please download the attachment and install it as per the given instruction)
To uninstall an existing SDK, you have to tick on check box of the SDK and click 'OK'. You will be able to the status in the modus console window.
To install an SDK you have to select the required SDK file from your computer by clicking 'Install Custom SDK' and Click OK. You will be able to the status in the modus console window.
When did you get this error message (attached pic in your question)? Did you uninstall both the default SDKs? We will try to reproduce this error at our side and will check whether it is an expected error or not.
"As a suggestion, maybe for folk like me say "tick to Remove" and this would be clearer." -> Thanks for your suggestion. I agree with you. 
Thanks,
-Dheeraj
