Why?

Because it is illegal in UK, France, Germany, Italy, Malaesia, and many other countries to have any suckers in the driver view area, hence the windshield.

No GPS, phone, anything, or they want your money for trespassing the law.

So how do we do than? Some dashboards are shiny enogh to hold a cup sucker, sorted. Most are not shiny, on the contrary, they have a texture of some kind, no vaccum cup holds on them.

So we go classical, with four bolts we can fast to anywhere (prefferably a bit hidden) the dashboard holder, actually more than one in various places might be a good idea, just print a few more, since to fit them you actually have to take down the dashboard cover...

Than according to our needs we can print a few clip inserts, the female type with two hinge pipes, a few different other male hinged attachements like another clip, or a straight nut, or a 40 degrees nut, or the 90 degrees nut, as per your needs, and fit ti into the female hinged clip with an M5 bolt, a few washers and a nyloc nut, that you can tighten untill the hinge is locked in the desired position (you might have to insert a few washers to shim if the male to female gap is too large)

Do not forget to put the big nut on the sphere before hinging them together, just a warning...

Than you have the bolt sphere holder with a mounting plate, on which you can fit whatever, a smartphone holder, a tablet holder, a coffe cup holder, anything, before you tighten it witht the sphere nut in the desired position.

Whether you need the straight extension, the 45 dgrees or 90 degrees curved extension or else goes by trial and error, also for tablets I might suggest to use two holders horizontally alighend, those tablets are heavy...

Is there any other application except for cars? Just use your immagination, a screen to attach to your 3D printer occasionally, some other work related temporary attachement like lights, microphone, those gadgets can give you the upper hand in many situations.

3D printing settings

I always print tools at 100% infill, 120% flow and the layer width larger than the nozzle (0.4 mm nozzle I print it at 0.5 width and 0.3 height) at the hoter end of that material, to improve adhesion, eliminate air micro gaps, make the part more resistant in use, and yes, that generates stringing, but I set my slicer to comb inside over the infill, so some of it is taken care of it this way.

BEWARE: In the summer in any parked car with windows closed temperature may rise up to 70 Celsius.

What this means, well PLA and PETG or ABS or HIPS are not a good solution since their glass transition temperature is less than 70 C, hence they will become soft and deform themsleves into uslessness.

You want higher glass transition temperatures materials, like Nylon, Policarbonate and anyway something that can hold fast at 100C, this also means you have to print them at higher temperatures, so modify your printer to be able to withstand 300C nozzle temperatures and higher please.