The styling of thost things are actually browser defined. You can target the various parts though, do some googling but here is one example. It might be possible to add a tooltip purely via CSS, i.e by using e.g a :before or :after pseudo element and the content:"..." attribute, and then have it show if :hover
As a workaround for now (actually, I’d prefer this to a tooltip parameter), give this a spin:
<div title="Some long tooltip message that could be from a transclusion.">
<$range tiddler="$:/_RangeDemo/1" min="-1" max="10" default="1" increment="1"/>
</div>
If for whatever reason at all you would prefer not use the “div” html tags, you could always use a custom tag.
For example, with a custom tag like, not particularly fun/creative,“thistip”:
<thistip title="Some long tooltip message that could be from a transclusion.">
<$range tiddler="$:/_RangeDemo/1" min="-1" max="10" default="1" increment="1"/>
</thistip>
You could take advantage of custom tags to document what’s going on, and highlight a block of code.
<RANGE-WIDGET-FOR-SUCH-AND-SUCH title="Some long tooltip message that could be from a transclusion.">
<$range tiddler="$:/_RangeDemo/1" min="-1" max="10" default="1" increment="1"/>
</RANGE-WIDGET-FOR-SUCH-AND-SUCH>