Tab contents are added when KActivities::Consumer::serviceStatusChanged signal is fired which happens after the layout is set. This causes the window to be too small initially so a minimumSize is set manually.
This change also adjusts the column span to 2 for rows with a single checkbox. The contents of third column would be pushed outside the scroll area on rows where column 1 is the label and column 2 are the controls since the width of checkboxes in column 1 is too wide.
BUG: 398793