I use a lot of arrows to draw diagrams, often copy-pasting or duplicating to make new ones of the same shape/curve. I've found that, over time, the speed of this action slows down considerably. It is now to a point where trying to do that action causes Inkscape to freeze and often crash (mostly "too many heap sections"). Opening of the svg file with these types of diagrams also takes a long time (~5-10 minutes) whereas a new document takes about a minute. Deleting these arrow-curves can also cause Inkscape to not respond.
I think this is probably related to Bug #1550902 (Marker list gets filled up with duplicates (inkscape = 0.91)) and Bug #1506026 (Performance regressions with auto-updating marker colors (Inkscape >= 0.91)). My list of used arrow heads in the marker list is large (over 100 at least). Attached is a file with such an issue.
Currently use Windows 10 64bit, Inkscape 0.92.0 r15299
I have replicated the issue using Inkscape 0.91 on Windows XP computer and Windows 10.
I do NOT see the issue when non-capped lines are copied/duplicated; only when it has an end cap (arrow).
Just found a workaround: If I copy and paste the entire schematic into a new file, the problem goes away. The marker list goes back to the default set without duplicates. Copy-pasting is smooth again. Interestingly, the file size drops from 3 MB to ~250 KB, indicating that some sort of memory build up is an issue (or can become one).