This is where you configure settings for the simulation of Modbus slaves and their environment, for the interface to a Modbus master, and for logging of Modbus messages. Each of these settings can be accessed from their respective tabs (Simulation, Interface,Logging) on the Edit Settings... dialog. This dialog can be reached by selecting Settings → Edit Settings... on the menubar, or by typing Ctrl-W.

The list of items on the left side of the dialog indicates the panels that may be selected. Clicking on an item on the left changes the display in the right panel and highlights the list item. The higher level, branch items on the left offer a description of the leaf panels that they group. Clicking on a leaf item in the list will bring up a panel appropriate to its function.

Each of the leaf panels has an apply button, which may be one of Add, Delete, or Apply. With the exception of the Delete button, apply buttons are disabled unless you enter or select something that is different to the saved settings. Once the apply button is enabled, you need to press it to save your entries or selection. However, if an error occurs as a result of the entry or selection, you can not save it: a message is displayed in the status bar at the bottom of the panel, and the incorrect entry or selection is left displayed. There are a few exceptions to this, for example, incorrect entries are cleared from the Map Addresses panel and the apply button is, accordingly, disabled, but the error message remains to be viewed.

If the apply button is enabled, therefore, it indicates that you have an unapplied edit - either due to an error or due to it never having been applied.

Closing the dialog discards all unapplied edits, but moving from one panel to another, or doing something else in the main window, leaves them visible (should you return to the panel), but not saved. This feature can be useful to enable you to check settings in other panels, or load a configuration file from the main window, before applying some edit. For example, while adding a register, you may need to check the range of addresses in the Map Addresses panel before entering a register address.