Filter that excludes matches from multiple cells

A few years ok, the paucity of available information (especially from Microsoft) as to which functions employ implicit detection of the last-used cell within the range referenced was such that you could perhaps forgive the widespread use of passing entire column references to functions which don't benefit from said implicit detection. Array formulas and SUMPRODUCT seemed to be particular favourites.

Now, however, people have started to cotton on to how bad a practice this is, and you can even find official documentation from Microsoft on the topic.

That said, I've seen comments from some to the effect that their super processing speeds make such concerns irrelevant to them. I consider my PC to be reasonable in that department, though a quick test involving copying the formula from post #1 (which has to process more than 31 million cells - for a single formula a record for me) to a mere 50 cells persuaded my version of Excel to pack it in for the day.

Regards

Originally Posted by Astromanatee

Of course, I don't fully understand your formula, and would like to.

D is the sorted list of all the unique values in column H?
X is the array of set themes?

Yes, that's correct.
I fully concur with XOR LX's comments re: entire column referencing and, tbh, if we knew more of your setup we would probably restrict the FILTER in the first instance (and/or consider using a Table object / structured references).
Above aside, based on the info available, the suggestion was to break the calc into 2 parts such that the "more expensive" MATCH calculations were only performed as many times as was strictly necessary - i.e. per unique (valid) value in H

edit: I should add, it doesn't matter where the SORT is applied, be that D or the final FILTER; the UNIQUE, however, should always be applied to D for the reasons outlined above