The construction package should be added as a style package to the document where you want to use it. If the ts file is in the right location, it should appear under Document->Style->Add package (or click the “plus” icon in the toolbar).
where I rebuilt the whole enunciation menu, as I did not see a way to insert a new menu item between already-existing items.
I also place construction inside the remark-tag group to get construction into the menu where one can cycle between the environments.
By the way the new enunciation menu works only if I am placing its definition after the lazy-initialize-force function call. In https://texmacs.github.io/notes/docs/new-lists.html I wrote the menu redefinition for the new list item without lazy-initialize-force; as far as I recall it worked, I will check then report/change the blog post if it does not.
Is it ok to always use lazy-initialize-force in redefinitions? Does anyone know?