There are any plugin/macro/something to create giveaways automatically?

Creating automated content is forbidden according to steamgifts ToS

https://www.steamgifts.com/discussion/MfCsX/tool-or-script-for-quick-mass-giveaway-creation like this?

This script is pretty perfect when you have everything in Excel like I do:

https://greasyfork.org/en/scripts/14840-steamgifts-ga-creator

The names of the games need to be exact enough for the Steamgifts script to recognise them; no change there as that also is the case when creating them individually; the add-on will tell you which games it could not find.

The only thing to keep in mind is that it creates a new tab for every giveaway so look at your popup blocker setting. Personally I do them in batches of twenty.

Don't forget that there is a large list of 'banned' games that you can't create a giveaway for. This page has an unofficial list: https://www.steamgifts.com/discussion/pJRbR/can-we-have-a-list-of-games-that-cannot-be-created-as-giveaway-unofficial-list-inside

I copy that list to Excel once in a while and use that to automatically show which games I can't create anything for. The list isn't perfect though.