Less colloquial version of "(X), never mind (Y)"?

As an alternative to never mind (which, by the way, I’ve never seen written as one word), you could use let alone:

In chapter 7, it was found that PV installers do not interact frequently with geographic data within their assessment, let alone with 3D geographic data.

Note the following additional suggestions:

1. In rather than From. You could say: Recall, from chapter 7. But it was found in chapter 7 that such-and-such.
2. A comma after assessment, to separate the subsequent phrase, which adds a further thought to the sentence.
3. Repetition of with before 3D ... data. Otherwise, a reader unfamiliar with this topic (e.g., me) might (and indeed did) think that the missing preposition is the more nearby within, which then requires some mental back-pedalling.

"Not to mention ..." "Even if we do not consider ..." "This is even more true for ..." "And especially ..."

Besides previously-mentioned phrases never mind, let alone, and even less, consider still less. (For example, replace “never mind 3D geographic data” by “and still less so with 3D geographic data”.) Phrase not to mention might also be used here by some writers, but is ambiguous in this context.

I personally would go with something like:

0) In chapter 7, it was found that PV installers interact rarely with geographic data within their assessment and even less often with 3D geographic data.

Or possibly:

1) In chapter 7, it was found that PV installers do not interact frequently with geographic data within their assessment nor obviously with 3D geographic data.

But maybe it is more common in math to say that things are obvious. Maybe if you want to test your readers' Latin:

2) In chapter 7, it was found that PV installers do not interact frequently with geographic data within their assessment nor, a fortiori, with 3D geographic data.

(I actually kind of like this one.) I think, if you are trying to be careful and precise, it isn't exactly clear how some fact can be truer than another. I also think there is some structural confusion from negating interact, but if you really want the original kind of structure:

3) In chapter 7, it was found that PV installers do not interact frequently with geographic data within their assessment and even less so with 3D geographic data.

But I think it would be better as:

4) In chapter 7, it was found that PV installers interact infrequently with geographic data within their assessment and even less with 3D geographic data.

P.S. I always say and write nevermind as a single word.