I have VG fir trim all over my house. It was installed pre-finished. 6 years later the nail holes that were filled with putty are showing up really prominently. If I do a light sand a put a coat of Spar Varnish on the trim, will the nail holes disappear and blend in again?
Depends on why they are showing up. Is it just color matching or are they somehow raising up? If it's color matching, I doubt just sanding and putting another coat of clear on top will fix it. Clear is clear. You might find some stain that hides them better and apply that with a tiny brush or similar.
Maybe, maybe not... :)
Fillers of any type rarely, if ever, will fade same way as the other material.
If the effect is only on the surface you might get it back close(r) again that way, if the filler has color-shifted to some depth, then it won't. We have no way to know what was used nor how it has aged from which to guess.
As another said, you may be able to touch up again if they're now lighter, that'll be somewhat harder to manage if they're darker than the surrounding wood surface.
You'll just have to pick a not-too-prominent area and do some experimenting to see what might be the result...
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