Triangular wave to sawtooth wave
If you mean gradually change triangle form to sawtooth, with same amplitude/frequency, then I think a variation on the classic op-amp triangle wave circuit can be a starting point, but it distorts the frequency. You could replace R2 with a bridge and two current sources?

Here I_1 controls amplitude, V_IN controls level.
For a symmetrical wave, V_MID is mid supply, but you can vary V_MID to change ratio of rise rate to fall rate. Here's a falstad simulation to play with.