My system simply assigns the same primary tool number but a different offset number to each tool in the gang.
Normally I call the tool nearest center T101, the next one T111 then T121 and enter the tool offsets on line numbers 1, 11 and 21. With a single tool post that would be all I use but I also have machines with the four place toolchanger. When I have multiple tools at different positions I just change the first and last digit in the number, for a tool at position 4 it would be T404, T414, T424 with the offsets being entered on lines 4, 14 and 24.
An open mind is a virtue...so long as all the common sense has not leaked out.