Inconsistent behaviour wrt Alt-0xxx key sequences

On the left-hand Tag panel the Windows-defined Alt-0xxx key sequences (used primarily for accented characters) are not accepted as input in any of the combo boxes. This is also the case in e.g Quick Action->Replace. In contrast on the main panel right context menu Rename these key sequences are accepted. The actual sequence I used was Alt-0233 for é (which I just used in this post)

I just used that in the tag panel with 3.16 and the result is this:

the é in Michél was an e before.

I also tried it in the Replace action with no problems

I use the Alt sequences very often, and do not have any issues. I am at the latest version 3.16 (64) now.

My bad - my keyboard doesn't have NumLock indicator. When I tried to do the accented charaters it was obviously off. It works fine with NumLock on. (Useful tip - get the Logitech app and turn NumLock off permanently which I have now done)
However playing around raised another issue - the Convert & Action menu have shortcuts of the form Alt-n. Is it by design that the n is only accepted from the alpa keyboard and not from the numpad? Atom. Notepad++, Sublime Text and Word will happily accept either the numpad or alpha keyboard numbers

See the keyboard shortcuts

and perhaps that what you used is already assigned to a different function like change the order of files in the file list.

For those in a similar situation:
There is a small free tool called "Keyboard Indicator". You can download, unzip and start it. Whenever you press the CAPS Lock or NUM Lock or SCROLL Lock or INSERT key you hear a click sound like from a picture camera. In the lower right corner you can see what special key you have pressed and if its ON or OFF.
There are settings to adjust the time this text is visible, the color and so on.
Just check it out, it works with WinXP / Vista / 7 / 10.

Source code is also available here.

If NumLock is off then the non-numeric functions on the keypad (Home, End,Pg Dn ...) are non-operative, so Alt-1 will always be "1" not "End". If NumLock is on then of course press the 1 key will generate Alt-End.
There is nothing in the linked document that show more than one function attached to Alt-1

I just found this:
keyCode is different for numbers on numeric keypad and numbers on top of keyboard.

keyCodes :

numbers on top of keyboard ( 0 - 9 ) : 48 - 57
numbers on numeric keypad ( 0 - 9 ) : 96 - 105

So it's not the same.

You are correct the raw key values are different. With app SharpKeys I mapped Num 1 (00-4F) to Key 1 (00-02) and lo and behold Alt-(Num)1 behaves just the same as Alt-(Key )1 and brings up the Convert dialog box. You also get the side bonus that Shift-Alt-1 produces the exclamation mark !. In this day and age this kind of low-level fiddling should be unnecessary. As with all text editors 00-48 and 00-02 shoild be mapped at the application level to Ascii/Unicode 0x31 the number 1

I doubt that.
It just as well be that these keys are deliberately left without function so that future functions could be mapped to them.

On most sites describing the method for inputting these Alt characters is strictly by using the number pad, not the standard upper keyboard number keys. I assume it is for this reason. The alternative method of course is to use the Character Map app, which functionally allows you more flexibility with the ability to search for characters by name, and insert multiple characters by the copy/paste method.