Since it's not actually part of the the literal text itself (I will go into that in more detail later), the tense it uses doesn't matter.
But you need to make sure of the subject-verb agreement.
Since it's list (singular) you need to use something like:
is going here
will go here
will be going here
Generally speaking, instructions like this are phrased in the present tense:
This end up.
Insert flap A into slot B.
Write your answer here.
But there's nothing wrong with using a future tense if you want to specifically convey something about the future.
That aside, another problem with the sentence exactly as it's written is that if it's taken literally, it would be interpreted in this way:
The flaws include but are not limited to: (1) the list of defects goes here.
Here's what's wrong with that:
- A list almost never contains a single item.
- You have used the word flaws (plural) at the start of the sentence but only provided a single item after the colon.
Instead, it seems obvious this sentence is not supposed to be taken literally. What follows the colon is meant to be a placeholder instruction in a kind of fourth-wall discussion between author and reader.
The common stylistic device for doing that is with square brackets.
As per The Chicago Manual of Style (17th ed.), 6.99:
Square brackets (often simply called brackets) are used mainly to enclose material—usually added by someone other than the original writer—that does not form a part of the surrounding text.
“They [the free-silver Democrats] asserted that the ratio could be maintained.”
“Many CF [cystic fibrosis] patients have been helped by the new therapy.”
Satire, Jebb tells us, “is the only [form] that has a continuous development.” [This was written before the discovery of the Driscoll manuscript.—Ed.]
So, I would write your sentence like this:
The flaws include but are not limited to: [the list of defects goes here]
This indicates that the sentence is not finalized and that it will eventually look something like this:
The flaws include but are not limited to: balance, durability, and complexity.