The sequencer GUI rendering performance is bad even in the small scenarios (Like one transform track recorded for 1 minute).
It is relative easy to optimize to run consistently at 60fps on even low end computers. (I did this in my own custom engine build of 4.13)
But the way the sequencer is currently iterating over the data every frame is making working with it difficult. Sadly upgrading my solution to the latest engine version is not trivial - which is why I have not created a pull request yet. It would be great to see someone taking a crack at that.
My initial modifications when I first discovered some of the bottlenecks can be found here:
Sequencer rendering of little white bars is insanely slow
However this was more of a quick hack than an actual solution to the problem (The actual drawing of the keys for example is also really bad… etc.)
To see the issue:
Record a cube for 1 minute that is constantly moved around by being dragged for example.
Open the sequence in sequencer and expand everything. Activate the viewport FPS so you can see the performance.
Some images that show how bad the performance is with varying levels expansions and clicking objects etc. can be found here:
This was done on the latest Razer blade.