The Index

Adobe RoboHelp 2019 has one index that is used for all outputs.

Click the keyword icon in the left toolbar (shown here with the names extended) and click the + icon to add keyword, then right click a keyword to add topics.

When you right click a keyword, you will see these options.

Apply a Condition Tag to exclude a keyword from a particular output.

You can also see the keywords in the topic properties.

You can delete a keyword here but you cannot add new ones.