I'm playing with the advanced genetics mod and I would like to sort out some items exclusively in this mod. After 1.7, I found that the item tree doesn't use numerical ID anymore, and I have no idea how to find the ID of the item I would like to sort in the mod, any help?

Unless TMI/NEI work and have been updated to show it, I don't know of any way currently to get mod item/block Ids except asking the author of the mod. (They should probably be documenting these because they are the same ones you need for reference in commands now too)

If it's not too much trouble you can install bspkrsCore. It will dump all IDs into UniqueNames.txt.

may I ask what is the point to use text IDs instead of numerical IDs?

The numerical ones change to match a loaded word or joined server now so
they are not consistent.