When editing Sharepoint forms with powerapps the Save and cancel buttons are not shown so we cannot test our forms in the designer.
Pleas add the save an Cancel buttons to the designer for powerapps forms.
Agree with this 100%. And this will be especially important if we get control over how the buttons are to appear when the form is published, as I posted here.
@RussellGove as a workaround you can add a custom data card and then add a button to it, and then OnSelect on the button to "SubmitForm(SharePointForm1)". That works from preview mode. You just have to remember to hide/delete the data card before you publish.