I'm playing a ribbon world (128 tiles height) with this mod. As I pan the viewport around, it gets 'stuck' on the edges of the world. This means that I can't zoom into tiles near the edges (top and bottom) of the world.

Try to replace charted function in control.lua (lines 501-503) in your save .zip with:
local charted = function(x, y) return player.force.is_chunk_charted(player.surface, {x, y}) and (player.force.is_chunk_charted(player.surface, {x - 2, y - 2}) or not player.surface.is_chunk_generated({x - 2, y - 2})) and (player.force.is_chunk_charted(player.surface, {x - 2, y + 2}) or not player.surface.is_chunk_generated({x - 2, y + 2})) and (player.force.is_chunk_charted(player.surface, {x + 2, y - 2}) or not player.surface.is_chunk_generated({x + 2, y - 2})) and (player.force.is_chunk_charted(player.surface, {x + 2, y + 2}) or not player.surface.is_chunk_generated({x + 2, y + 2})) end

This is interesting. I'll look into it, and maybe incorporate this change.

Thanks @sladki - that's done the job for me. That's a big improvement ;D

This way of checking this is a little bit of a kludge, but (AFAICT) guaranteed to work by the normal chunk generation rules (i.e. a 3x3 invisible radius of chunks is always generated around any charted chunk). I'll make this fix and upload it shortly.