List abs are very good for list and table manipulation.
I often use "array get" to get table data and make a list out of it and then use list-abs to do some manipulation, like reverse, invert, replace, add elements and then "array set" to put it back in the table. So many options with that library 🙂
I did find a couple of already compiled externals, like sexy, cyclone ans else. Sexy I used to use a lot.
But these days, I try to make everything vanilla, for ease of use.
For reverb I really like Freeverb. I found this, but it seems like it's not compiled specifically for Bela, but "just" for Linux:
Maybe I'll try to follow the compile instructions for Bela and see if I can compile it sometime 🙂