Help identifying circuitry diagram
Looks like that board is the &quot;Presets switchboard&quot;.  The long rectangular boxes are multi-pole switches.  I'm quite sure they're radio buttons (only one active at a time).  Depending on which is pressed the components on the other circuit diagrams will get different values.  Exactly which values are set by which button are shown in the table on page 1.  For example, the first three columns show how each button affects the value/state of R1, R2, and S10 in the V.C.A. Envelope Generator circuit (on page 3).  If, e.g., the &quot;Piano&quot; button is pressed then R1 gets the value 33kΩ, R2 is 0Ω (i.e. directly connected), and S10 is on (connected).
I've taken another look at things and it looks like the top switch (by the dual connectors) is the &quot;off&quot; switch; it contains S1—S8.  The remaining multi-pole switches control each preset (as shown in the table).  I think the bottom one on the picture (by the single connector) is &quot;piano&quot; and the second from the top is &quot;synthy&quot;.  There is no circuit diagram provided for that board; it would probably be a good idea to draw one before proceeding further.  One other aside, I think R4 is always 100kΩ (the notes are a bit hard to read).  (Further edit: the additional photos you added match the above)
I think the most challenging part of the repair will be sourcing replacements for the damaged switches.  That kind of part is very hard to find.  If I were in your situation I'd probably just design a replacement board using 8 momentary push buttons, resistors, a regulator and a bunch of 74-series ICs (latches, etc.) for logic, relays for the audio signals, and maybe some LEDs or bulbs for indication.  Alternatively, and easier for a beginner, you could use an SP8T rotary switch, some resistors, and some relays. Lots of ways to approach it...