Today I altered the schema for a connector and thought I should also alter the transformations before saving my changes. I though about clicking the Save data button before I changed tab.- But, I figured the system should warn me about saving the data if the data is not saved when switching tabs. So I did not save mu changes before switching  No warning came and when I got back to the schema all the previous fields I had de-selected were now selected again. That's about 20 min wasted time. 

You should have some sort of check mechanism activated if changes has occurred in the schema section before switching tabs if changes have not been saved.