I wish there were some kind of settings menu where you can change things like the range for the item magnet can pickup items.
Or have it as a proper data pack instead of a Jar file so I can change it manually in the file.

I have had plans to make a settings menu for a while, that maybe be added in a future update

As for this being a "proper datapack", both datapack zips and mod jars are available on Modrinth: https://modrinth.com/datapack/jakes-build-tools/version/1.9

Oh, missed the data pack section. I just selected Fabric and got the Jar file
I was thinking of extracting the data folder in the Jar file

For now, if you want to increase the distance by modifying the datapack, you can do so in "data/jbt/function/magnet/effect.mcfunction", change the 7 in there to whatever distance you want

Just be aware that the magnet does operate without line of sight, and making the distance too big may cause issues with game performance

I'm so used to mods on Modrinth so I just automatically choose Fabric and the game version.
I used to have a different data pack called Magnet Mode.
You used the /trigger command to enable and disable it.
But that data pack stopped working in Minecraft 1.21
It's a really old data pack, but it's been working up till now.

https://www.curseforge.com/minecraft/customization/magnet-mode