Just a quick video on how to add manual supports in Cura (Version 3.21)

Automatic support generation works great in Cura, but sometimes you just want to add support at some place without changing the supports for the whole project.

The key is to load an additional object - a simple cube is what I use - and define the area where it intersects with your model. That area can have totally different support parameters.

Step 1: Load in the Cube

I have a simple cube that I scale to the desired shape. Place it where you want the extra support.
Under the leg in this case.

Step 2: Change the Cube to a Support Definition

Cura offers a selection to "print as support". That will print the whole cube as support. We just want the area under the leg within the cube. So choose that setting from the drop down menu.

Then the parameters you want to change. Use the search bar on top to get the support options.

A support angle of 0 degrees will effectively support everything, change to whatever you need.