Theorem numbering

In the manual there is a note on how to change environment numbering in the article and amsart styles. Here is where it is mentioned:
Standard TeXmacs styles (FSF GNU project)

It says

If you use the number-long-article package, then the numbers are prefixed by the section number.

However there is no mention on how to use packages. There is an option under Document->Style->Add Package however in the drop down list there is nothing like number-long-article. Here is a screenshot:

The only way I found to change the numbering is to go to Document->Style->Add Package-> Add other package.... and write in the name of the package manually. This seems to hinder discoverability. Is this intended? Am I looking in the wrong place?


I did not look through the menus for the number-long-article package. As far as I know, the only person now composing packages and styles for TeXmacs is Joris van der Hoeven (the other members of the “core team” are involved with other parts of the code)—to ask him if this is intended, it is better to do it through the mailing list. Again AFAIK he reads rarely the forum.

Said this, I also find that the discoverability of TeXmacs—in general—is insufficient.