@paddyclown Je suis sceptique quant au nom de la route. J’ai habité à Lyon dans la rue Voltaire pendant 3 mois. Mais c’était il y a vingt ans. Il n’y a manifestement pas assez de temps pour apprendre les subtilités des conventions d’appellation françaises !
Is this the gist of what you’re looking for:
Ooh, mais parfaitement ! Well done, this looks fabuleux !!!
Eh bien, puisque vous le dites ainsi, je suppose que je vais continuer. 
According to the IFC, the house is on bull excrement street and things are going very well! *Tip of the hat to @ateliernab for his translations.
What kind of sorting by ifcClass did you have in mind? Like with like?
Yes, the idea is to do two main things.
1- be able to select for example all the ifcWalls etc
2- see what components have not received any class.
This second one is particularly useful as whilst modelling we may forget to classify as we go, and then it’s hard to know that we forgot.
What I do now is export to ifc, open in a viewer, then go through the objects that got exported as ifcbuildingelementproxy and in // on a second screen go through the outliner and reclassify as needed.
Being able to do this in SU would be such a boon !
It helps that we have a quite sophisticated nomenclature system in place for objects, but again, we’re human and sometimes forget to name correctly even if we’ve classified properly.
Hope that makes sense ?
Yeah, that makes sense. It sounds like what you are looking for is a no-fuss, no-muss, easy searching, sorting, and filtering solution that removes the need and worry of relying on fragile mental lists and tedious multiple application import/export cross-referencing processes that require a dual monitor set up -and presumably copious amount of coffee- just to get the proper classifications you and your clients rely on daily for your work using the nomenclature you’ve developed specifically for this purpose. Or just a boon if it’ll do.
Let’s make a friend of simplicity, shall we:
You can see the filters can show what has and doesn’t have IFC types. With searching IFC you can find all of what has which type. There’s nothing I can do (or would do) about having coffee on hand for any of this.
Eh?
Also, a point of clarification. You used the term “class” above. But are these ‘really’ Types? The Entity Info panel, Advanced Attributes, display these in the Type field. So it seems to me these are (schema) Types. I used “class” at first and then changed it in the code because “type” seemed to be correct. Which one is correct or makes the most sense in use?
Wow !
That’s stunning 
You’ve hit the nail on the head there. 
So, I say “classes” as that’s what IFC is all about.
It’s in the name 
Industry Foundation Class file.
However, in the inner workings of SketchUp maybe that is translated as a Type variable ? I’m sadly not familiar with how SU stores the “class” that we attribute to a given component…
Indeed, it probably stores it under Type, but I’m afraid it’d be someone familiar with the under the hood workings who’d be able to tell you !
In any case, your video shows something that is very close to what I had in mind 
I’m glad it’s getting closer. I was concerned it was missing a note .
Okay, let’s just say we’re showing ‘classification types’, so using the label “Type” in the extension is fine for now. All is good .
I would say something like, 'In the IFC 2x3 classification schema, the data contains Types (e.g., ifcObject, ObjectType, ifcLabel, etc). So, for me something is an ‘Object Type’ or ‘Type’. But in plain English (and I guess by convention in other languages), people say ‘it’s classified as an XYZ’. Or put simply: ‘it’s the XYZ class’.
Il ne faut pas chercher la petite bête!
I would like to iron out the code a bit and send the extension to you, if you’d like to test it. We could find out if it updates properly in a real-world workflow …find out if it works when the rubber hits the road. Find room for improvements if needed. I saw posts to the Forum saying the EW is behind on reviewing extensions, but the goal would be to put it there soon.
No need to nitpick over these beastly little details! Eh? 
oh, playing with semantics usually ends badly, so…
I’d be more than happy to road test this as it is !
Many thanks for spending time on this, it’ll be a real help I’m sure