You can use the Generate Bracing in Cells function to quickly create diagonals for beam structures. The members must form a so-called "cell", that is, an area in a plane formed by four corner nodes and enclosed by members on all sides.
You can access this feature by selecting Tools → Generate Model - Members in the menu. The dialog box 'Generate Bracing in Cells' appears.
In the 'Bracing Member Template' section, define a template member whose cross-section and member type you want to use for the diagonals. Use the you can select the member graphically in the work window.
Then, click the button at the bottom of the 'Cells' dialog section (marked in figure above). In the graphic, all cells that the program recognizes in the model are marked with a cross.
Click the relevant cells one by one so that they are displayed in the selection color. Click OK to return to the initial dialog box.
The selected cells are included in a list. You can change the data here, if necessary. After clicking OK, the program creates the bracings in the specified areas.