You can load the dev version in your console for testing using load_all (or Ctrl/Cmd-Shift-L). It's better to leave a functional version of vignettes in the repo rather than something with hacks for your dev workflow (better to adjust the workflow so the hacks are not needed).
You shouldn't need to do this:
https://github.com/MUCollective/multidy/blob/6c0e7b472ca268ca0906983f1e6472a75fc4871d/multiverse-custom-code-chunk.Rmd#L16
(and elsewhere in the vignettes)
You can load the dev version in your console for testing using load_all (or Ctrl/Cmd-Shift-L). It's better to leave a functional version of vignettes in the repo rather than something with hacks for your dev workflow (better to adjust the workflow so the hacks are not needed).