rubbing wear of the wiring harness behind the dashboard

Wrap the individual damaged sections with self amalgamating tape, then over-wrap the unprotected section with something to protect it, like ordinary tape that can be removed if you have to access individual cables later, and perhaps use cable ties to carefully pull it out of contact with the area rubbing

Just be aware self amalg tape bonds to itself very strongly - so don't over-wrap bunches of wires you need access too

Or use a wrap protector like spiral wrap, it is easily removed in the future.

Sealey does proper fleece tape; looks ace, or try their silicone self amalgamating tape; cleaner than rubber.

https://www.sealey.co.uk/product/5637188917/19mm-x-15m-fleece-tape---black

https://www.sealey.co.uk/product/5637201956/5m-red-silicone-repair-tape

Can recommend the self amalgamating silicone tape that Ewan linked to. Used it to great effect below on long range WiFi transceiver connectors on a sea going boat. Much cleaner to use than the black stuff.