I've only browsed this book a few times, so am not an expert on its contents.
But for a start, there are some 3000 figures. Eliminate those that show steps toward completing the knot. That may cut out 1000 or so. That step is relatively easy.
Eliminating duplicates that are tied by different methods, such in a bight v. an end, would be desirable, but may be more work. I know for example that the two versions of the 'shake hands loop' are on different pages. Unless Ashley or someone else cross references cases like this you might miss the duplication.
Any further weeding probably requires defining what makes two knots different or the same?
The bowline/sheet bend family was mentioned. It makes sense to distinguish between the uses for nets (load on all for ends), for loops (load on 3 ends), and bends (load on 2 ends). These knots are consist of an interlocking bight and loop. But with the sheet bend, does it matter which end of the bight is loaded? On the bowline, the consensus seems to be that strength is the same whether the bight puts the free end on the inside or outside of the loop, though one may be more prone to snagging. On the other hand, which end of the loop is loaded seems to matter. The Eskimo Bowline (as in Budworth) is distinguished from the bowline by the fact that bight wraps around one of the loop legs rather than the standing end. I don't recall seeing an 'Eskimo sheet bend'; the load is always on the end of the loop that exits through the bight. [unless Budworth's 'Complete',p35, reference to a 'false sheet bend' under Lapp Knot qualifies]. Plus there are variations of the sheet bend in which the bight is replaced by a spliced eye, or a slit in (leather) strap.
When tying a bend, there are, in theory, 4 possible loadings (end 1 or 2 of rope A, end 1 or 2 of rope B). Symmetry may eliminate some choices. Stability may eliminate others. For example, a square knot loads the two 'bottom' ends (right-left symmetry). When I try to tie a version that loads diagonally opposite ends (bottom on one side, top on the other, diagonal symmetry), I get a knot that rolls when loaded. I don't know if Ashley bothers to include that insecure version or not.
paulj