<$button>
<$action-createtiddler $basetitle="title" tags="person" name={{temp!!name}} surname={{temp!!surname}} />
Create
</$button>\define fullname() {{temp!!name}} {{temp!!surname}}
Then use <<fullname>> at the title
Tony
<$vars fullName={{{ [{temp!!name}addsuffix[ ]addsuffix{temp!!surname}] }}}><$button><$action-createtiddler $basetitle=<<fullName>> tags="person" name={{temp!!name}} surname={{temp!!surname}} />Create</$button></$vars>My next suggestion would be triple curly braces and a filter like yours.
Thanks for the correction.
Tony
{{{ "Mr "addsuffix[ ][{temp!!name}addsuffix[ ]addsuffix{temp!!surname}] }}}{{{ [Mr ]addsuffix[ ][{temp!!name}addsuffix[ ]addsuffix{temp!!surname}] }}}but they didn't work.