Simulate capacitor discharge in Qucs
One of the really cool lumped components in Qucs is a time controlled switch.
You can specify the initial value as open or closed (see below), as well as a list of times when the switch should change state. Example of how it's used.



Actually, the time-controlled switch is really a time-controlled two-state resistor with default values [Ron=0 Ω; Roff=1e12 Ω].

You can choose any value for Ron and Roff. Combined with the list of times when the state changes, this a powerful and easy-to-use  time-controlled element in simulations.