Integrate external docs in toctrees

[pde...@gmail.com]

dear all,

AFAIK, one cannot integrate external docs (to the current folder) in toctree, for instance (in Myst), this directive doesn't work, but it's pretty frequent that one have to refer in an index, when managing multiple folders, to an external file (thru intersphinx); the only solution is to mix toctree directives with {doc} or {ref} ones, which are not similarly left-aligned (see this doc. : https://inspe-sciedu.gricad-pages.univ-grenoble-alpes.fr/gene/)

```{toctree}
---
maxdepth: 1
---

<other-repo:file>

```

So, two questions arise:

- If Sphinx developers are stumbling upon this post: would it be possible to add this option in toctree directives;

- I noticed this extension, external-toc from executable-books: https://github.com/executablebooks/sphinx-external-toc ; didn't tried so far but anyone did? does it fulfill this purpose (toc-trees external linking)?

thanks for your answer,

best,

ph