Tested only on linux. Though it is Conda/Python stuff so prolly works on Windows as well.
I had a reason to filter out dropped/planned/held series when I transferred my list from MAL to AniList, which is why this script exists.
# Download/init MiniConda under ./conda. Activate the conda environment.
. init_conda
# Filter an exported MAL list in.xml -> out.xml.
# -p -w -c -d and -H correspond to 'Plan to Watch', 'Watching', 'Completed', 'Dropped' and 'On-Hold'.
# Leaving out the respective flags makes the corresponding entrie to be left out from the out file.
# -n <num watched> keeps the series if it has more than <num watched> episodes watched regardless oif the other flags
./mal_filter.py [-p] [-w] [-c] [-d] [-H] [-n <num watched>] in.xml out.xml