Fixed tabs are the tabs that do not scroll along with other tabs when pressing the scroll buttons. Fixed tabs are by design the nr. of tabs starting from the (first) leftmost tabs and this number of tabs is set with AdvOfficePager.FixedTabs. If you want two non scrolling tabs at the left side, set AdvOfficePager.FixedTabs = 2.
I tried that. Does not work as expected. I am still able to move the tabs.
It was not clear you referred to tab reorder instead of scrolling.
We've investigated this and seen an issue with setting AdvOfficePage.Locked = true. This is fixed now and setting Locked = true will allow you to prevent reordering a tab associated with the page.