Once you have 15-20 Tactics editing the Tactics in the Tactic Profile preference Dialog (reached via the Event-B-> Sequent/Prover -> Auto/Post Tactic" pane) becomes very, very slow. It takes minutes for Rodin to respond after pressing the "Finish" button after editing a tactic. Redrawing the Tactics list can also become very slow; taking now several seconds for each Tactic, i.e., 2-3 minutes or more in total to redraw the Auto/Post Tactic window.
I could not reproduce this bug with Rodin 3.5. The UI remains quite fluid. I suppose that it has been fixed in between.