For demonstration purposes I’ve performed a similar task on the ribbon cable for a cracked nintendo switch LCD but it’s the same principle. Unfortunately, i don’t have a camera for my optical microscope, so you’ll have to settle for these poor quality phone shots, as i say though, this is for demonstration purposes only and was the culmination of about two minutes of work after purposely severing the cable, I would in no way consider the joints here as acceptable…for example i didn’t even bother changing my tip (using D24 chisel tip) whereas you’d want to use a finer point tip.
In this case, i just repaired the three larger traces on the ribbon for ease and demonstration but you’d do it to all 6 of your severed conductors on your ribbon.
Intentional sever/tare
Scratching back the Kapton esque polymor coating revealing the copper traces using X-acto/scalpel
Flux, lots of flux
Tin with leaded solder, re-flux as required.
Select an appropriate sized conductor to bridge the break, use a strand from multi core cable, ensuring diameter of strand doesn’t exceed trace width.
Then solder the wire accross onto the tinned ribbon traces being careful not to bridge to the trace next to it. In your case, I’d recommend repairing the finest traces first, then applying UV mask, then coming back after and finally doing the larger traces, this will reduce the risk of knocking your previous repair off or bridging. I’ve highlighted the conductors I’ve repaired/bridged here as it’s not clear from the photo because of quality.
Next you want to test that the traces aren’t bridged from one to the other and that theyr’e making it from one side of the ribbon all the way to the other, do this by measuring the corresponding trace pad at the end of the ribbon in contunuity mode on a multimeter
If all is good then finally you can coat with UV curable conformal coating and cure.
Hope that helps, It’s recommended that you practice first on a scrap ribbon from something else if you haven’t done this before and get some practice in