No matter what I do, I can't convert belts. I put a belt of e.g. rare quality on the ground and select it with the conversion tool. the message "convertet 0 entities" appears in the chat. :C

I found and fixed the issue for myself 2 min ago. The conversion list is being populated in a function that is only called the first time the mod is run for a world so if you ever save and load the list will be empty.
There is likely a better way to do it but for myself I added code to check if the list is nil when you try to convert and if it is to build the list. Don't know how to contact Anitone other than posting here and wouldn't want to hijack the mod by posting an edited version especially when all I did was spot and fix an issue and couldn't have made the mod myself.

I found and fixed the issue for myself 2 min ago. The conversion list is being populated in a function that is only called the first time the mod is run for a world so if you ever save and load the list will be empty.
There is likely a better way to do it but for myself I added code to check if the list is nil when you try to convert and if it is to build the list. Don't know how to contact Anitone other than posting here and wouldn't want to hijack the mod by posting an edited version especially when all I did was spot and fix an issue and couldn't have made the mod myself.

Hi there. Thank you for your time, you managed to fix mod a bit. Mod is not actively developing right now, and, i guess, it wont be updated soon, feel free to fork/modify or rewrite structure. I dont really know i just have no time to deal with development. Also ill add a discord username in my bio (if anyone whenever will need this again lol)

Anyway you can make you own mod or i can invite you as collaborator to this mod. Write me down any time if you want.

I have posted a version with the conversion fix and supports bobs logistics.

Link to the version I posted
https://mods.factorio.com/mod/belt-quality-quickfix
just added option for underground belt distance