if you just want to make the tabs visible to certain users only (if your users don't have the ability to view the script or add fields to the GUI and thus see data they're not supposed to)
=> Then you can do without SA. Just use the OSUSER() function to identify which user is logged on and set visibility_conditions for the tabs.
That of course depends on how your users access the apps - if they access them via the Browser, they cannot do much beyond selecting anyway, so that will be all right.
If they have the client, you have to use SA to mark them as "user" (as opposed to "admin") and take from them the ability to open the script and to add new objects.
then it's quite easy: In the Browser the users cannot do much beyond selecting and clicking - they cannot access the script by default and they cannot add any fields that you haven't made available - so you are the gateway to pass if users want anything new.
That limits your "ToDo-list" to adding visibility_conditions to your sheets using the OSUSER() functionality. Just try it out in a textbox so you know the syntax.
And in case you have the tabs (on the top) deactivated and you have navigation buttons, apply the same conditions to those so the users don't see buttons that don't do anything - that's always a bit irritating.
Section access is not needed in this case. As stated above, all you need is the conditional show of the sheets, and condition is based on the current user. See sheet properties, tab General, check "Conditional" and enter condition.
For Tabs 1 and 2:
wildmatch(OSUser(), '*User1*')
for tab3
wildmatch(OSUser(), '*User2*')
for tab4
wildmatch(OSUser(), '*User3*')
If there is a tab available for user 1 and user 2:
wildmatch(OSUser(), '*User1*', '*User2*')
In all examples, "user N" is Windows ID of the user.
