It really depends on how many of these you have and what you consider “manual”.
Manually using the “edit citation” options you could hide the author (no need to hide the year, since there isn’t one, but it might be cleaner) and enter exactly what you want to appear in the citation prefix (abbreviated author name) and suffix (, type in the accessed date).
I actually prefer to make the endnote version hidden text, and use the text to create my altered version, as plain unhidden text. This way, I can see the original endnote citation, if I want to. the Hide author and year above is more or less “invisible” until you modify it.
(Aladin – Website of the ALADIN Consortium)(Aladin – Website of…2017-01-18) (where the underlined is endnote and the text following is your manual insertion, just using word.
Finally, if you have many, you can choose to modify the bibliograph’s web template or a new custom template just to handle those without a year, exactly as you want them to appear. It would require putting the abbreviated author in Author, and the accessed date in year, so the citation template would give you the correct items. Then custom or other author fields to report the full author name in the bibliography and the year is now after the words “accessed on”. Webpages or other resources that have a year or aren’t too long, would still be marked as the normal ref type. This is probably pretty complicated as you have 2 parameters to accomodate.