When exporting a timber model from Frame Analysis to Timber Member Design not all sections are available to choose when in the design tab.
Sections are added to the list by going to 'Edit Timber Grades (F5)' under the input tab. When clicking on the F5 button the 'Timber Properties' dialogue box will open. The value in the 'Size Number' columns in the first tab (Timber Grade) corresponds to the column under se 'Section Sizes' tab. Thus, the sections written in under each of the 5 columns will then show up depending on the Timber Grade that you have selected.
You can now enter custom section sizes in the different columns by clicking and typing in an empty line.