I just realized I made a mistake. See this:
Contrats is a Tab in a Tab control, and the mistake is that portal PortalContrats should have been located on the first Panel of the Slide Control.
I try to drag PortalContrats below the first Panel, but that does not work, event though the Side Control is not Locked.
I use FMPA 17.0.4 under High Sierra.
Why can't Move the portal ?