John K Jordan
Looks interesting to work on!
I have used all kinds of things to hide tiny lines and voids. If a bit of chip is missing, I have whittled a sliver and glued it in with white glue. If there is a fine line in lighter wood with the edges darkened too much with glue I might remove the dark part with a #11 scalpel first.
If the line is clean but visible because of a tiny valley, I usually sand some similar colored wood and press/wipe fine sawdust powder into the line and solidify with glue, often CA glue. I use a capillary tip on a bottle of fine CA, or if that drops too much glue I might put a drip onto something then dip a needle point into it to transfer just a few molecules at a time!
A line of glued sawdust can stand out if it looks too even, so sometimes I'll use a couple of different sawdust powders arranged to create "grain". I have even resorted to painting some variability on top of the line to hide it, using the Faber-Castell Pitt artist's pens/brushes.
If perfection is not needed but it just needs to look ok, the wax scratch-filling crayons for furniture can work ok.
A coincidence, but I'm about to repair a hand carved fork and refasten a carved llama that broke off the top!