Here are two ways there may be more:
1) you can use two lfos start with basic patch:
lfo1 = triangle, frequency 100, amount 0, dest: osc all freq
lfo2 = square, frequency 15, amount 127, wave reset on, phase 80, dest: LFO 1 Amount
this makes lfo2 turn up the amount of lfo1 after about 5 seconds (and off again after another 5)
2)you can also use the sequencer start with basic patch:
lfo1 = triangle, frequency 100, amount 0, dest: osc all freq
sequencer = play source: key, env trig/step: off, clock divide 1/2, bpm 120
track select 2 and set the dest to lfo1 amount, set step 5 to value 127 and tie to the end step 16
this makes it when you press a key the sequence starts and after 5 sec the lfo1 amount kicks in