improved: add/change to start of .replit:
onBoot = '''/nix/store/fbi9r30p3lqk96lmw5b1v1bpbj62cr2l-inotify-tools-3.20.11.0/bin/inotifywait -rqme create --format=%f%w --include='\..+\.py.[0-9]+~' .|while
read f
do
f=${f#.}
o=
r=
while
read -r l||[ "$l" ]
do
case $r
in
"")case $l
in entrypoint*)m="${l%\"*\"}\"${f#*~./}${f%.*~*}\""
case $m
in
"$l")break
esac
l=$m
r=1
esac
esac
o="$o$l
"
false
done<.replit||echo -n "$o">.replit
done'''
And run kill 1 in Shell.
This will map the entrypoint to the last file you edited through the IDE.
Replace .+\.py on line 1 with the ERE of the files you want to be auto-set as entrypoint.
(I tried an option which checks for you just visiting the file in the editor but I found that that’s impossible. Maybe you can do this with an extension)