Hebrew word search: How to search a root word in all its various permutations?

The morphologies are different takes on the Hebrew Bible by different people/groups. Each one has a slightly different philosophy of the Hebrew language and categorizes it differently. I recommend going to the Morph search, selecting each morph, type @ to bring up the Morph picker and explore how that particular resource classifies the Hebrew language. I am most used to the Westminster 4.2 morphology, but I'm starting warm up to the Andersen-Forbes especially since the syntax resources use that morphology.

When it comes to searching Hebrew texts I don't know how to catch all the variations on a single tri-consonantal root because 1) I t think all of the morphology schemes sketch lemmas differently between Nouns and Verbs (i.e. as 3MS Qal and 3S Nouns). 2) The texts differentiates between homophones.

What you could do is Look up the root you want in the BDB, find all the relevant forms and run multiple searches. Alternately, in the morph search, type: h:qd and look for all the lemma forms that are appropriate (lemmas are indicated by English glosses). I ended up running four searches

lemma:קָדוֹשׁ
lemma:קדשׁ
lemma:קֹדֶשׁ
lemma:קָדֵשׁ.1.n (no results in Isaiah)

Hmm. Didn't recognize this capability.  Are the words with an English word next to them pointing out/designating the root words (in your example, 'holy', 'raging, onrushing')?

The English glosses indicate lemmas, however, typing h:qdw only gets you part of the way there. Since Logos recognizes multiple transliteration schemes the h:**** syntax  produces a list of possible matches that you have to scroll through to find the appropriate match in the case of h:qdw it misses other forms of that tri-consonantal root, most notable the verb meaning "to be holy"! That is why in my example I omitted the w and was able to find more appropriate lemmas.

Go to Morph Search, select BHS / WHM 4.2 and Westminster Hebrew Morphology. Type h:qdw (or h:qadosh) in the Find box, from the dropdown select the word with "holy" against it. You should then see  lemma:קָדוֹשׁ, which is the root word.

I know very little about Hebrew, so could be way out in left field here, but wouldn't the one above the one marked "holy" actually be the root word since it doesn't have any vowel pointers?

Here's another suggestion. If you have a Hebrew keyboard installed you can type lemma:קדש and get this:

Then the English glosses should show you all of the lemmas which are a subset of the tri-consonantal root.

May I ask how you came to know about the functions such as typing @ in the search bar? Are there any more of these little tips that helps to define searches?

I don't remember exactly where I learned this, but it is documented in the Help file. It's also documented on the Logos wiki. I recommend http://wiki.logos.com/Search_HELP as a basic starting point for learning how to use the Logos search engine.