I've been contending with some personal issues and have mostly lost track of the three project assistance projects in which I'm involved. This means that it's critical to drop back to a single project in single assistance mode. Are your posts 37 and 38 referencing two different parts?

For #37, it appears that the code is missing the axle hole. You'll want to use the code I posted that includes module solids() and module holes() and the difference() feature. That one should have the necessary lines to generate the axle hole.

You ask in 37 if you should update Cura and I think that's a good idea. Also, because the part is going to have overhangs (the entire disk), you will have to enable the support feature in Cura. Due to the layer structure of 3D printed objects, I would cut the model in half with a plane on the z-axis and print it in two pieces. This eliminates the need for support and also places the layer lines in a much stronger orientation.

Another question I think you've asked is about the axle diameter being 1.9 and the hole being 1.95 mm. This is a good idea but should also include creating a test part to determine how well that will work. Be sure to increase the diameter of the outer structure. I called it axle_diameter in the code, but it's obviously not the axle diameter of the metal part on which the pulley rotates.
Code:
$fn = 90; // smoother surface of cylinders
axle_diameter = 2;
axle_hole = 1.5;
disk_thick = 1;
disk_diameter = 10;
short_stem_height = 2;
long_stem_height = 5;
stem_diameter = 2;
groove_radius = disk_thick / 3;
addabit = 0.0625; // provide overlap to avoid z-offset
abitmore = 2; // ensure overlap for difference operations
arbitrarily_large_block = 20;
half_a_block = arbitrarily_large_block / 2

module solids(){
    cylinder(h = disk_thick, d = disk_diameter); // main disk
    translate([0, 0, -short_stem_height + addabit]) // move short stem below disk
    cylinder(h = short_stem_height + addabit, d = stem_diameter); // short stem
    translate([0, 0, disk_thick - addabit]) // move long stem above disk
    cylinder(h = long_stem_height + addabit, d = stem_diameter);
}
module inthegroove(){
    rotate_extrude(convexity = 10)
    translate([disk_diameter / 2, 0, 0])
    circle(r = groove_radius);
}
module holes(){
    cylinder(h = disk_thick + short_stem_height + long_stem_height + abitmore, d = axle_hole);
    translate([0, 0, disk_diameter / 2 - short_stem_height + disk_thick / 2])
    inthegroove();
}
difference(){
    solids();
    translate([0, 0, -short_stem_height - abitmore / 2])
    holes();
    translate([0, -half_a_block, -half_a_block])
    cube(arbitrarily_large_block);
}
Here's the last code I created. If you intend to increase axle_hole to 1.95 mm, there won't be enough material remaining to print the axle_diameter of 2.0 mm. You'll want at least two nozzle widths around the hole, more is better. Change axle_diameter to 2.0 plus 0.4 * 4 (1.6) which will make it 3.6 mm. If you can get a 4.4 mm or 4.8 mm to fit, that's even better. Size matters.

Earlier in this message, I suggested that you consider to chop the object in half in order to print it for better layer line orientation. I know at least three ways to accomplish this and can probably think of others. Two involve Meshmixer and Fusion 360 and it's entirely possible that Cura will allow it as well, but I'll stick to OpenSCAD to improve the confusion factor.

Notice that there are two new lines in the difference() feature, as well as matching lines at the top of the code, to define the parameters.
half idler.jpg

You can now use Cura to drop the flat surface to your bed, rotating it appropriately for better printing. Do NOT use manual rotation, use the "drop to bed" feature in Cura, which will ensure that all surfaces are flat on the printer bed. As this is an exact chop in the middle, you can simply print two of the same, to glue together and create a far superior model from a strength standpoint as well as removing the requirement for supports. Ensure that you have supports turned off inside Cura.

If I can get my head together, I'll address the other model, if I am able to remember. The next couple of days are going to be challenging and by the time the weekend gets close, I'll have forgotten.