There isn’t a way of doing this as such within QuickFile, but there are workarounds. Depending on your situation, they may work for you.
As you mentioned, projects is one way of doing this, which is touched on here: Projects - opening balances (ringfenced funds)
Another way would be to use a dummy bank account in QuickFile, which although it’s a little older, the concept is still the same from this thread: Ringfenced funds
The latter method could potentially make reconciling your bank account a bit trickier, but it would give you a clear breakdown of what’s available and what’s been used.
Aside from this, this is an open forum, so other users may also have ideas which can help. We’ll leave the thread open for others to jump in, too.