Q: I've noticed a setting labelled 'Growth is Fixed', under Advanced Settings > Growth (& Yield) - what does this setting refer to?
A: When using any of the software's market-based functionality, i.e. when you are trying to introduce some element of volatility into a plan, it is assumed (in the first instance) that any accounts entered via the Savings screen are exempt from any volatility, on the grounds that they are most likely to be deposit-based, rather than investment-based, accounts - as a result, they are unlikely to be vulnerable to short-term market fluctuations, and this is what the 'Growth is Fixed' setting refers to.
So, while this setting exists for all Savings/Investment/Pension accounts, it is - by default - only ticked for accounts entered via the Savings screen. For investment/pension accounts, therefore, growth is not fixed, meaning that these accounts will be subject to any market deviation being modelled. One does reserve the the option, by the same token, to check this setting, in order to exempt any specific investment/pension account (e.g. a 'structured' product), if appropriate, when modelling a market fluctuation.