This might work, but I think it is best to not tinker further if you already have a working script (especially one that you understand and can modify further if needed).
perl -pe 's/\[[^]]+\]\((?!https?)[^#]*#\K[^)]+(?=\))/lc $&=~s:%20|\d\K\.(?=\d):-:gr/ge'Hmm, OP mentioned "Only edit what’s between parentheses" - don't see anywhere that whole URL shouldn't be changed...
Here's a solution with perl (assuming you don't want to change http/https after the start of ( instead of start of a line):
perl -pe 's/\[[^]]+\]\(\K(?!https?)[^)]+(?=\))/lc $&=~s|%20|-|gr/ge' ip.txt
e flag allows you to use Perl code in the substitution portion.\[[^]]+\]\(\K match square brackets and use \K to mark the start of matching portion (text before that won't be part of $&)(?!https?) don't match if http or https is found[^)]+(?=\)) match non ) characters and assert that ) is present after those characters$&=~s|%20|-|gr change %20 to - for the matching portion found, the r flag is used to return the modified string instead of change $& itselflc is a function to change text to lowercaseGNU datamash (https://www.gnu.org/software/datamash/alternatives/) - handy tool for data munching. There's also https://github.com/BurntSushi/xsv
Check out my chapter on GNU grep BRE/ERE for those wanting to learn this regex flavor: https://learnbyexample.github.io/learn_gnugrep_ripgrep/breere-regular-expressions.html (there's also another chapter for PCRE)
Memory, Sorrow, and Thorn by Tad Williams
I use Vim ;)
Python itself provides IDLE, which is good enough for beginners. https://thonny.org/ is another good one for beginners.
As mentioned by others, Jetbrains is good for many languages. https://www.kdevelop.org/ is another option.
I have a list of learning resources for CLI tools and scripting here: https://learnbyexample.github.io/curated_resources/linux_cli_scripting.html
I've also written a few TUI interactive apps to practice text processing commands like grep, sed, awk, coreutils, etc: https://github.com/learnbyexample/TUI-apps
Why do you think it is a phishing link? Gumroad is a well known platform to sell digital goods.
I mention it is free up to some date because it will go back to being a paid product after that.
Well, I'm not going to even try understanding the various features used in that
sedcommand. I do know how to use basic loops with labels, but I never bothered with all the buffer manipulation stuff. I'd rather use awk/perl/python for those cases.