Edit Inside

While you can connect and manipulate objects inside the group, if you try to add another object to the group or delete object from the group, it wouldn't work.

Instead of ungrouping and then grouping the objects again, you can work inside the group. Look at the bottom of the workspace there are two tabs.

Click on the Edit Inside tab. Now you can add or remove objects inside the group. When done, click on the Main Flow tab to return.