Change gear cables for Shimano Tiagra 4603
manual is here
https://si.shimano.com/api/publish/storage/pdf/en/dm/ST0001/DM-ST0001-05-ENG.pdf
exploded diagram here
https://si.shimano.com/api/publish/storage/pdf/en/ev/ST-4603/EV-ST-4603-3155.pdf
all via si.shimano.com
Video for similar shifter