The SVG viewer "inkview" is not just slow, but takes QUADRATIC CPU time.

Tests with files zipf-test-time-{k}.svg generated by gnuplot:

k      N       T T/Q
- ------ ------- ---
1   5000   3.533 1.2
2  10000  11.624 1.0
3  20000  54.354 1.2
4  40000 309.863 1.7

where 
N = number of points in plots.
T = cpu time of inkview (seconds).
Q=2.9*(N/5000)^2.

Inkscape 1.1.2 (0a00cf5339, 2022-02-04)