Currently there is only option in configuration to treat recommended and suggested packages as dependencies. It is too simplistic - there is no information about recommended and suggested packages and no option to select some of them explicitly. I'm used to good Synaptic's solution where package context menu show lists of recommended and suggested allowing for selection.
Muon is no longer maintained, please switch no a supported alternative like https://apps.kde.org/discover/ or the package manager native no your system. Sorry for the inconvenience.