There are two ways to set the default topic: You can choose it directly in the TOC, or you can specify it by its topic ID in the project configuration options.

Setting the default topic in the TOC

To do this just right-click on the topic in the table of contents and select Set as Default Topic in the context menu:

Once you have set it, the default topic is indicated by a green arrow icon (the green check marks you see in the example are for version control status):

Setting the default topic in the configuration options:

If you are only using one TOC in your project you can also set the default topic the project configuration options.

In the Project Explorer on the left, navigate down to Configuration > Common Properties > Language Settings. You can then set the default topic by selecting its ID. (If you need to locate the ID select the topic in the TOC first and look in the Topic Options tab on the left of the editor window.)

Note that this setting will generally only apply for the main TOC if you have defined multiple TOCs in your project. See the section on default topics in multiple TOCs further below for details on this.

If you use the default topic setting in Language Settings you can also use a user-defined variable instead of selecting the topic ID directly. (This variable must insert a valid topic ID, of course.) This makes it possible for you to change the default topic at publish time by changing the definition of the variable.

Important: Variables can only be used for the main TOC

Since this setting is only used for the main TOC, you can also only change the default topic with variables for the main TOC.

If you are using multiple TOCs in your project you can set a separate default topic for each TOC. Then you will automatically get the correct default topic for that TOC when you use it.

Important: The default for secondary TOCs must be set in the TOC
Default topics for secondary TOCs must be set directly in the TOC. The setting in Configuration > Common Properties > Language Options is only for the main TOC.

Each TOC you define can have its own default topic:

Help+Manual allows you to combine multiple projects in modular help systems and each project can have multiple TOCs, each with their own default topic. This means you can have multiple default topics defined, but your output can only ever have one default topic. The right one to use is chosen as follows:

In modular projects only the Master defines the default topic

In modular projects only the default topic defined in the Master project is used. Any default topics set in child modules are always ignored, because child projects can be excluded.

Logic for choosing the default topic

1.If the current TOC has default topic defined it will be used.

2.If the current TOC has no default defined, the default topic defined in the main TOC is used.

3.If the main TOC has no default topic defined, the default topic defined in the Configuration > Common Properties > Language Settings. If nothing is defined there, the first topic is used.

4.If the Language Settings option is used, resolve any variables used there and use that topic if the result is a valid topic ID that exists. If the topic does not exist or is not included use the first topic in the current TOC.