If-Then-Else in a Behavioral Voltage Source
That expression already works, as it is, in LTspice. The syntax is that of a ternary operator:
condition ? expression#1 : expression#2
which is the same as
if( condition, expression#1, expression#2)
And what you have there is a nested condition:
if(a, b, if(c, d, e))
There's no need to post any pictures since you can readily verify it yourself. In fact, I wonder why haven't you simply tried it? It's not like the computer's going to catch fire.
What jonk mentions in the comments is also true: depending on your application, the discontinuities brought by the conditional may, or may not affect the convergence. If you find that's the case, don't use a voltage source (bv), use a current source, instead (bi or bi2), with:
I=&lt;expression&gt; Rpar=1 Cpar=10p
Adjust as necessary.