Hi Helyx,
As a rule, BEYOND use logic "function of time". Classic math example... Position=Amplitude * sin (Time*Speed). This logic is foundation of BEYOND effects. As a rule, in default state Effect has not state. So, look at this as on function. OK, see, if to change value of Speed in this formula, then it will cause jump, quick change of Position only because you changed the speed. I am sure you see what I mean. That is why change of speed will not work as many peoples expect. For stateless effects the answer is adding of acceleration control, an additional waveform that will modify the time. Or a use of Channels, hehe, this is a bit complex theme, Main idea - to do no use time, instead of it use Channel, and then modify this channel by means of other effect.
The is ability to try and see how change of Speed will work. If assign Identifier for Effect (see Effect properties), then Effect will be Public object and can be controlled from script, as well as by means of Object Animation key effect. This is new thing, not well tested. I think it should work on timeline.
Timeline of BEYOND support set of ST2000 effects. These effects can be added by means of main menu Effect. One line represent one type of operation. There is option "relatively to current value". Give it a try. It might be a simple answer.
What I wanted to recommend originally. Each Track can include many Effect lines. You may use one Effect with multiple Items inside it, or many Effect lines with simple Effects inside them. Result is equal, but you have more freedom. This will allow you create 3 effect events like:
[ some effect before ]
[normal] [faster] [normal]
[ some effect after ]
Best Regards,
Alexey.