Tabs
There are design programs that can automatically add a tab where desired (although the default size may not be what you ultimately want). Silhouette Studio is not (yet) one of those programs. Fortunately, the mechanics of adding a tab are not onerous. The more important decision is where (and whether) a tab is needed.
When two elements are to be joined, only one element needs a construction tab. A rule of thumb is to make all the tabs lie in a consistent direction. For instance, on four separate walls of a house put a tab on the left wall of each element. This rule works in most instances, but there are cases where the designer must alter that rule. If a cut-out window lies where it will be impinged on by a tab from an adjoining side, it would be wise to decide to put that tab on the side with the window so that it can glue to the other element where there is more space. This may affect the placement of all the tabs (if one wants to keep them all pointing the same way) or one element may ultimately have a tab on both the left and right sides, and another element may have no tabs on the sides.
The size of the tabs can be affected by the ability of the builder. For example, a child may do well with a 0.5 inch wide tab, while an experienced builder may prefer a 0.25 inch tab. Some applied elements (like a step unit or a shed roof) may themselves be small, so a smaller tab is necessary.
A tab that is a mount for the main building onto a base can be wider. Conversely, a tiny joint (such as a short chimney shoulder) may do better with no tab at all if it is supported on either side by tabbed joints.
Method for making tabs:

- Start with the basic element. This one needs tabs on the left (by convention), on the eaves (for under-roof construction) and on the lower edge (for mounting on the base).

- Draw fold lines over the element outlines. In this example, the fold lines are slightly outside the main lines for visibility. They should be drawn directly on the lines in an actual design.

- Select the main shape for point editing. Place additional points where needed, then pull the solid line out to make a tab.

- The completed tabs: