Yes, unlike boolean controls, indicators have not all those fancy mechanical actions, as indicators are supposed _to_indicate_ the values on theirs inputs. But you can implement your required latching programmatically - with a shift register (if in a loop) or with a local variable of this indicator. In both cases just perform a logical OR operation with old value. So once set to TRUE, the indicator will remain in this case (just don't forget to initialise it to false in the beginning).