This is definitely something that needs to be addressed in my opinion as well. We model many structures in which contractors specifically ask/need us to provide the alignments at the Centerline. Concrete box trenches as one example. Understandably, the solution is currently to create a secondary alignment to control the outside edge at 90deg corners, but that introduces extra work that should not be necessary. "Extrude element along a path" can model 90deg corners so templates should be able to as well.

If you control the linear template from the outside point it will make a angled corner. For the the curb and gutter the control alignment would need to be the lip of gutter.

I agree with you about the sidewalks. But my main problem is with the curb and gutters (see images).

I'd do a linear template for the curb and gutter, then a terrain/surface template for the sidewalk. The sidewalk is more of an "area." I'd check your slopes on the back of the sidewalk if the point control is set to "horizontal" and not "both.

Maneged to get the result I want through adding point controls to one of the template points and refering an aux line. But, as my previous comment, would be really a lot of work. One that could be an drop option. Adding some links so you can see other people have are in this same situation and from what I read, older versions had something to what I´m suggesting.

https://communities.bentley.com/products/road___site_design/f/geopak-inroads-mx-openroads-forum/228575/corridor-template-drop-corner-behavior/707245

https://communities.bentley.com/products/road___site_design/f/geopak-inroads-mx-openroads-forum/241327/corridor-pi-rounding-tangent

Could work, but would be really troublesome to do this to every curb element. We work on industry size projects with kilometers of curbs+gutters.
And the surface tamplete wouldn´t allow me to create a complex curb/gutter geometry (attach), only "boxes".

A linear template probably isn't the best option for this case. I'd use a terrain model and a surface template.