I'd like to connect GOTEK to CDTV [...] but not sure where are all the signals and how to wire it up.
Simply connect either side according to names - they are the same on both sides, aren't they?
Signal CDTV Gotek
/CHNG 11 2
/MTRX 8 4 /MTRON
/INDEX 22 8
/RESET 10 --
/SEL0 21 10
/SEL1 9 12
/SEL2 20 --
16 /MTRON
/DIR 19 18
/STEP 18 20
/WD 17 22
/WE 16 24
/TRK0 15 26
/WPROT 14 28
/RD 2 30
SIDE 13 32
/RDY 1 34
but I can't find schematics for cable.
Maybe because it's straight forward? Commodore didn't invent the floppy, they simply worked with what was there, and noone likes to make complex cables. If you flip either connector upside down, you will notice that the sequence is the same on both sides, so a flat ribbon will do most of the work.
Where are the missing signals that I can't pair between amiga external drive connector and gotek drive?
Gotek is build after Standard (PC style) Floppies which use only 2 select signals (no need for SEL2) and don't feature a RESET.
MTRX/MTRON are the same signal, Motor-On. For PC style floppies there are two motor signals, but Amiga only supplies one - which doesn't really matter for the Gotek, so both can (should) be bridged.