Works fine

Note: that sort of tooltip is formatted by the OS and browser and using such a small font size that it is hard to read.
The problem is not limited to this tooltip but all over J. Maybe it is possible, in another PR, to increase the size with a specific js?

I have tested this item ✅ successfully on 2e0cb63

Maybe it is possible, in another PR, to increase the size

No its a native browser setting and we should not change those.

I personally would prefer something more "styled" than just using the title tag.

In principle it works, I see the tooltips. But the title shows:
<a id="menu-collapse" href="#" class=""> <span id="menu-collapse-icon" class="fa fa-fw fa-toggle-on" aria-hidden="true" title="JTOGGLE_SIDEBAR_MENU"></span> <span class="sidebar-item-title">JTOGGLE_SIDEBAR_MENU</span> </a><hr />_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/27347.}

@ChristineWk
it is translated here.

Aha :-) ... Is it successful now? - even I see above title: JTOGGLE_SIDEBAR_MENU

I have tested this item ✅ successfully on 2e0cb63

The reason of wrong translation was: I hv beta-dev from october, but there is: 4e7bc1c.
Finally I changed all above files accordingly.
<a id="menu-collapse" href="#" class=""> <span id="menu-collapse-icon" class="fa fa-fw fa-toggle-on" aria-hidden="true" title="Toggle Menu"></span> <span class="sidebar-item-title">Toggle Menu</span> </a>

RTC

@brianteeman
I see no way to modify admin-menu.js (and metismenu) to get what you propose.
As far as I understand, you propose https://mm.onokumus.com/mm-vertical-hover.html which is very different from what we use today, as it is unrelated to our menu toggle.
If you do not propose some code shortly, I suggest we merge this.

@infograf768 no need to touch any js at all see #27352

Both PR's work for me, this one here and @brianteeman 's #27352 . Not sure what's the better way to do it regarding all aspects, but from a visual point of view I really like Brian's solution. It really is nice.

Closing in favour of #27352