Even if/though such measures are not essential, they are, nevetheless, desirable.
Those measures are desirable, even if they are not strictly necessary.
We would like those measures, even though we don't really need them.
2. There's also another meaning:
Those measure are desirable; they might even be essential.
Those measure are possibly essential. Even if they aren't, they're desirable"
Usually the context, or the tone of voice, will determine which is the intended meaning.
"Caramel topping on ice cream is desirable, if not essential." Meaning 1.
"Wearing a helmet when riding a motorbike is desirable, if not essential." Meaning 2.
Also, you might not know whether something is essential or not: "Wearing a helmet while riding a motorbike in Australia is desirable, if not essential." In fact, in Australia wearing a helmet is required by law. It is essential. So, this sentence has meaning 2.
Do you have enough context to work out which of the two your sentence means?
Student or Learner