Allocate Object Type to Layer
The Import|Options for ... dialog offers to identify layers of the imported data with the respective object types. The allocation list can be saved to a file for reloaded (button „Open“). CadnaA will interpret all data lines belonging to a single layer as objects of the allocated object type.

Click once in table column „Layer“ and press the F2 key to switch to Edit mode. The insertion mark appears enabling to type in the layer designation when known. Up the 127 characters can be entered.
When the layer designation is unknown double-click into a row. On the Import: Layer dialog, either enter the name/s of the layers containing the object type data or select one of the available layers from the list box. The list box lists all layers as defined in the respective import file.
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If several layers are to be identified by common character strings, you can also use wild cards, such as *, to substitute arbitrary strings (see CadnaA-manual "Attributes & Abbreviations").
Example
Roads A through F are on layer STR1, roads G through M on layer STR2. You can import all of the roads A through M at once by entering STR* in the Import: Layer dialog for the object type Road.
If roads A through_ F_ were to lie on layer STR1, and roads G through M on layer ROAD, roads A through M could also be imported all at once by entering "STR1|ROAD" (i.e. STR1 "or" ROAD) in the Import: Layer dialog for the object type Road.
This "allocation list" can be saved to a file for subsequent re-use by clicking the Save AS button, and can be opened again (Open button) as required.
The data will be imported after confirming with OK.