regarding "AttributeError: ‘QWidgetItem’ object has no attribute ‘itemAtPosition’ ".
this is a bug in kapiyas official version of this plugin that shows up when the plugin tries to hide some buttons in the brush preset chooser based on their location in the ui. i guess the layout of the widget changed at some point on the way to krita 5 so the script can’t find those buttons anymore.
i have made a patched version that you can download here:
youll probably have to delete the files of the original kanvasbuddy from your krita resource folder before installing my patched version though.
in my version i also fixed some issues with icons that changed in krita 5 and added keyboard shortcuts for switching to the different dockers (default is shift+1 through 9).