How do toggles work?
If you set up a connection, then you will always have the possibility to toggle your Mappings on the right hand side. By Default they will all be toggled on. The screenshot below indicates a regular connection with the Mappings all toggled on. If a Mapping is toggled on, then this Mapping will be synced.
As a user you can always decide which Mappings you want to toggle off. If a Mapping is toggled off, the field Mappings on the left hand side will automatically be greyed out. This means that these Mappings won't be synced.
If the Default Field toggles are not visible then you have been a PieSync customer for a while and are still working on our old engine. To make the toggle option accessible, remove the old connection and set up a new one to enable this feature.