In Windows 11, how can I reduce Explorer's columns to less than 170 pixels?

This. If you set the display to a Custom Scaling (under "Advanced scaling settings"), this disables (or changes to a more reasonable one) the minimum column width. However, if you change it back to non-Custom then it will snap back to the unreasonable minimum.

So: in OP's case I would suggest setting a Custom Scaling and seeing what happens.

(This just happened to me, as I'm on a PC with a nice 4K monitor I brought from home, and a 1080p one provided by the office. Setting custom scaling applied to both screens, making the 4K one too damned small, so I had to revert to non-Custom, and boom -- the columns went back to stupid sizing the second I played with them. I guess having more screen space is worth putting up with wasting some of it on empty column space. Win10 Enterprise 22H2 19045.4412)

You can set the default widths as small as you like via the registry, but they will snap back to their minimum setting if you move the column separator. The defaults are specified in em values, so it's a single setting regardless of your screen's scaling. The number of pixels is dependent on screen scaling.

You can set the column width defaults, and any other folder view defaults using a free tool I wrote called WinSetView. I can't say if it will help much in your case, as I do not use a tablet, but it's an option that you can safely try.

Perhaps my reply was too long or the screen shots somehow prevented my last reply from uploading, but I'm checking back in and it looks like I didn't post anything at all.

At any rate, the images I had uploaded showed a few screen shots of my Choisir les détails (Pick Details?) window that opens when you click on More after right-clicking on any column header.

One shows (showed?) all of the columns are at various widths from 449 (File Name) to 90 (État or Status?) before trying anything.

Another showed the result of attempting to modify any column width : I snaps to a new minimum of 170--this occurs whether click-dragging between columns or right-clicking and choosing Adjust Column Width or Adjust All... .

Another was a this screen shot of the column headers (Nom, État, Modifié le, and Type) illustrating how, for example, the Status/État column width is five times the length of the the word État.

Another screen shot showed that the monitor was set to recommended scale (100%) and resolution (1920 x 1080).

I also added that as I was doing this, I experimented with trying to change column widths on another screen in another File Explorer window. It worked "normally" (or as expected) allowing me to reduce column widths. I opened another and it went back to being uncooperative.

...except for when it does work.

It sometimes it works normally. Perhaps it has something to do with scaling. I don't think that 170 pixels should be 5 cm wide on any screen. (The column width is about 5 times the word État on my screen.)

Thanks, however, for the speedy reply at any rate.

Hi, I am Dave, I will help you with this.

In the new File Explorer app, there is no method, setting or known registry hack to reduce the column widths any further, that is set as the minimum in the coding of the new File Explorer app.