Need an expansive collection of schematic symbols
There is no comprehensive collection of ALL schematic symbols because there is no single "standard" for what symbols to use or for what they mean.  Most are made up as we go along and need new symbols for new things, or as understanding and formal organization of knowledge of circuit design and function evolves.  Certainly if you are limiting yourself to a single designer/manufacturer (such as Apple, etc.) then they likely have a "house standard" for schematic symbols which you can come to understand by simple familiarity.

The symbols you are asking about are generally known as "off-sheet connectors" (at least that is what I call them). They indicate that the signals go to some other board, or some other page of the schematic diagram collection of pages. 

In many cases, the shape is arbitrary and has no intrinsic meaning. But in your specific example, note that the shape of the "arrow" indicates whether the signal is coming "in" to the page, or going "out" of the page.  Or in the case of your example, the connections are clearly labled as "IN" and "OUT" and "BI" which means bi-directional (both in and out).  And in your example the numbers at the outside of the symbols likely are references to where you can find the other end of the symbolic "connection".