Maybe not necessarily a problem with the companion app itself, but rather with the webapp inside of it not functioning as it should.
Currently there is no possibility of removing a label from a selection of entities, firstly because the UI does not show the subwindow for the labels, but also because once you try to deselect the label [-], it turns into a checkmark instead, thereby adding the label to all selected, even though it should be removed. Even after clicking it again, the checkbox turns blank (as it should), but the labels remain.
Removal currently is only possible by remaking the label completely or going into the settings of each entity and deselecting it one by one.