Q. How do you show an investment bond that is in a trust?
A. There is no mechanism to designate a Bond (onshore or offshore) as being 'in trust'. Instead, choose the investment 'Type' as 'Other Trusts', wherein you can designate the investment as being within either a 'Bare' or 'Discretionary' trust. Having set this up as a Trust, the software will not, then, take any ad hoc withdrawals from the asset, for the purpose of meeting the clients' expenditure. If it is the case that the clients are receiving (some) income from the Trust, this can be scheduled via Advanced Settings > Liquidation Limits & Planned Withdrawals.
This will ensure that the proceeds from the bond remain outside of the estate for IHT purposes. Unfortunately it will not tax withdrawals from the bond in the same way that a bond would in the software so you may want to leave it as a bond in Voyant so that any withdrawals show correctly in the plan and from a taxes perspective.