Does anyone have a list of mangas where the mc transmigrated/reincarnated in an extra's bo...

Just from the top of my head, this:

https://www.mangago.me/read-manga/the_world_s_best_engineer/

And this:

https://www.mangago.me/read-manga/trash_of_the_count_s_family/

I have a action manhwa rec list, if you go to the Transmigration section there should be some under that category

https://docs.google.com/spreadsheets/d/1gcnYcgU9zDD9kCFjLHNEqjQ8qPzLEutsaezzAqYR9FY/edit