You can draw customized sheet metal transitions just by picking two valid entities.
For this particular case, the transition is defined at its base with a polyline that is made by one third of a circle, two lines from the arc ends to the arc center, all with a fillet radius, and a circle at the top.
First, main and branch transitions are created. Afterwards, they are trimmed to get the resulting 3D object.
Thus, the 2D contour development of the trimmer including the intersection hole, and the development of the trimmed object are created.
Video shows all this process and photos of actual object.
Our first example is a custom transition. We have 2 polylines at different heights. We start filling the sheet metal thickness and the folding radius, and then we pick the two polylines that define our transition, to get the unfolded development.
Our second example is a custom branch. Here we have two transitions that I have previously created with LITIO sheet metal. They intersect themselves. We first pick the trimming main, and then we pick the trimmed branch. We get the main with the hole, and the branch and its development.
Our third example is a custom profile. We start filling the thickness, the internal bending radius and the profile height data. Then we pick the 2D polyline that defines the profile shape, getting the profile and its unfolded development.
As a bonus I show the plane trim feature: we first pick the object to trim, in this case, the profile I have just created. Next, I pick the three points that define the cutting plane, to get the trimmed profile and the new trimmed development.