You can certainly put more than one tab panel on the same layout. The issue likely is with the tables you've defined for your data and how a layout can directly specify only one such table. If 'Project', 'Detail' and 'Documentation' are three different tables in your system, your layout can only directly refer to one of them. You can include fields from the other two tables on their own tabs, but now you must set up a relationship between these tables to control what data appears in these tabs. If you need multiple records to be listed in each tab, this can only be done by setting up portals in each such tab panel and each such portal also requires a relationship, which in turn controls what records will appear in the portal.
If you describe your system and what you want in more detail, we can probably suggest an approach that works for you.
This is obviously a bit more complicated than I had hoped and is gonna take some time to get right.
Got to stop work and have my dinner now, so I'll probably be picking up on this again tomorrow.